The ins and outs of discs, drums, shoes, and the hydraulic system: how your brakes protect you.

Brakes are as important as the engine of any car and they are essential to ensure your safety when driving. The basic principle of brakes is simple: they take the kinetic energy of the moving vehicle and transfer it into thermal energy through friction so that the car stops. All brakes follow the same principle, but different systems achieve this friction in different ways.

Many factors will determine the type of system your car has and the components it uses, as all systems vary slightly, but here are the systems your car is likely to have, how they work, and what the key components are likely to be. Understanding a car’s braking system and vehicle braking systems can be vital, so read on!

BRAKING SYSTEM COMPONENTS

Before discussing the type of system a car may use for braking, it’s worth mentioning the key components, especially if you’re considering repairing or replacing parts of the braking system. The types of parts your braking system uses will often depend on the car’s make and model, the speeds it can reach, the car’s price, and its age. A braking system will use a drum or a disc and will contain brake pads.

DRUM BRAKES

Drum brakes are the oldest way to stop a car. A drum is attached inside the wheel, and inside are two heat-resistant pads. When the pedal is pressed, the pads push outward and press against the drum, and the drum stops the wheel. The friction caused between the pads and the drum causes the kinetic energy to transfer into thermal energy.

These types of brakes were commonly used on cars until the 1980s. As cars became more powerful, drum brakes couldn’t meet the challenge of stopping them. They get very hot under intense conditions of frequent braking, and if they get too hot, they can’t convert motion energy into heat and they stop working. After the 1980s, many cars started using disc brakes instead.

This isn’t to say, however, that drum brakes aren’t used at all. They are still adequate and they do the job. They are often used for the rear wheel brakes, as when a car stops, most of the pressure is applied to the front brakes. Since drum brakes are cheaper to manufacture and simpler to maintain, they are often used on entry-level or cheaper models.

DISC BRAKES

Disc brakes are what “replaced” drum brakes as the most popular choice for most cars. Drum brakes push, and this doesn’t create as much pressure as squeezing the wheel. So experts designed a system where something is squeezed rather than pressed. They also discovered that a larger surface area also means more friction and is essential for improving braking at high intensities. The combination of finding something to squeeze and seeking a large surface area led to the adoption of disc brakes.

A disc brake is a mechanism to slow or stop the rotation of a wheel from its motion. A disc brake is normally made of cast iron, but in some cases, it is also made of carbon or ceramic composite. This is linked to the wheel and/or axle. To stop the wheel, a friction material in the form of brake pads is forced against both sides of the disc. The friction caused on the disc wheel will slow or stop it.

Some discs have modifications to ensure they cool faster and remain more effective. This is often achieved by letting air in, so modifications like a hole in the middle, small gaps around the outside, or fins will allow air to access the disc and ultimately mean a more efficient braking system.

BRAKE PADS

Whether it’s a disc or a drum used by your car, the main component contained in the disc or drum is a brake pad (sometimes called a “shoe”). These are what create the friction. Many different materials are used for brake pads, but some common pads can be organic (using glass, Kevlar, carbon, etc.), ceramic, semi-metallic, or fully metallic. All materials used are designed to absorb as much heat as possible.

Organic brake pads are very quiet and don’t wear the disc, but they need to be changed more frequently as they tend to wear out. Ceramic pads are also very quiet, last a long time, and have great braking capacity, much better than organic pads. Semi-metallic pads even exceed the capacity of ceramic pads, but due to the metal flakes in the synthetic material, they wear the disc more, so the brake disc will need to be changed more often. Finally, there are fully metallic brake pads.


This is what race cars use. They have incredible stopping power, but are noisy and will wear the disc like ice melting in the sun. Your car is likely to have synthetic or ceramic brake pads, and these are two good choices for everyday driving.

MECHANICAL BRAKING SYSTEMS

Mechanical brakes were the first of the types of braking systems installed on automobiles when they were mass-produced in the 20th century. These systems involved a series of pulleys, cables, cams, and other devices to apply friction to the brake drum and stop the car. When the pedal was pressed, it pulled on a cable, the “brake line,” which in turn forced the drum to press against the wheel and stop the car.

There were many problems with these braking systems. For one, they required a lot of maintenance because the brake lines and all other moving parts had to be kept in perfect condition for the brakes to work. When the brake cables were under too much pressure or the force required to stop the vehicle was too great, they could also break easily, and this would be very dangerous. The systems also needed maintenance due to their precision; if a lever was off or the cable tension wasn’t quite right, different wheels would receive different braking pressures, making the car very difficult to control.

Because of all these issues, by the late 1950s, mechanical brakes were rarely seen on cars, and they were replaced by hydraulic brakes.

That said, most cars still have a form of mechanical brakes: the handbrake. In addition to having main hydraulic brakes, cars often have a mechanical handbrake that uses a lever and an arm inside the brake drum to help stop the car. They are operated by a cable from the handbrake lever inside the car. A ratchet on the handbrake lever keeps the brake engaged once it is applied. A push button disengages the ratchet and releases the lever. All cars have a handbrake system (sometimes electric and not mechanical) that acts on two wheels – usually the rear wheels. This mechanical system is only meant to secure the car when parking rather than stopping it, so a mechanical system is suitable.

HYDRAULIC BRAKING SYSTEMS

The most common braking system for modern cars is a hydraulic braking system, and your car is almost certainly equipped with hydraulic brakes. Cars usually have this on all four wheels, and hydraulic systems can use a brake disc or a brake drum.

Unlike older mechanical braking systems, hydraulic systems use a fluid to apply pressure to the brakes. Hydraulic fluid is stored in the brake lines and is used to transmit the pressure or force from the brake pedal or brake lever to stop the car. Brake fluid, or hydraulic fluid, is a non-compressible substance that can operate at high temperatures and high pressure.

In this type of braking system, the mechanical force comes from the driver pressing the brake pedal. This force then pushes the brake fluid through the lines and, since it is not compressible, toward the braking system. In a device known as the master cylinder, this force is then converted into hydraulic pressure that is sent to the brake calipers or drum segments (depending on the type of system).

Each brake caliper contains a series of pistons (up to 6), and the hydraulic pressure forces the caliper to clamp onto the disc or drum. The brake pads attached to the brake caliper create friction when they rub against the brake disc or drum, and this is what ultimately stops the car.

Hydraulic braking systems also have distinct advantages.

First, the force generated in the hydraulic braking system is higher compared to the older mechanical braking systems used in cars. These are rather primitive and rely on levers, linkages, or cams, which don’t transfer as much force as hydraulic braking systems. Mechanical systems can also lose their efficiency over time as working parts break down.

The risk of hydraulic brake line rupture is very low, and they require very little maintenance, again in contrast to mechanical brakes. They are also incredibly fast and responsive to the pedal, and very little force needs to be applied to the brakes to exert pressure on the drums or discs.

Since a hydraulic system has far fewer moving parts than a mechanical system, the wear on these parts and any associated or resulting maintenance is also reduced. This makes the system cheaper and more reliable than a mechanical system. Since mechanical systems could also vary significantly in their design and construction from one car to another, this often made repairs tricky. Hydraulic systems have a relatively simple design and are easy to assemble, making maintenance easier.

SERVO BRAKING SYSTEM

Often also called power brakes, or servo brake or brake booster, a servo braking system is designed to provide additional power to reduce the effort needed to apply the brake and will work in conjunction with hydraulic brakes.

The brake servo works by creating a partial vacuum, which then increases the force applied to the master cylinder. With a brake servo, the brake pedal first presses on an attached rod, which then allows air to enter the servo while closing the vacuum. The pressure then increases on the rod that connects to a rod inside the master cylinder.

The brake servo became more common in cars as disc brakes replaced drum brakes as the standard setup in vehicles. Disc brakes require cars to be equipped with power brakes to eliminate the majority of the force a driver must exert to stop the car.

Inside the brake servo system, a vacuum multiplies the force exerted by the driver on the brake pedal. The outer aspect of a brake servo is a cartridge that contains a diaphragm, a valve, and is usually constructed of metal. Attached to the brake servo is also a one-way valve, which limits the direction of air to outward only to eliminate the risk of losing braking function while the car is operating.

If the vacuum fails because the engine stops, for example, the brakes still work because there is a normal mechanical linkage between the pedal and the master cylinder. But much more force must be exerted on the brake pedal to apply them.

The anti-lock braking system (ABS) is not only a crucial element of a new car’s safety system, it makes braking much more efficient and easier. Here is our guide to what it is and how it works.

Anti-lock brakes were first used in the 1950s, originally to prevent airplanes from skidding on the runway during landing. The hydraulic system reduced stopping distances during aircraft landing and the risk of tire blowouts. In a short time, engineers began to realize that this type of system could also make automobiles much safer.

Even for the most experienced drivers, roads can be filled with unexpected hazards that might force you to think quickly and slam on the brakes to avoid a collision or imminent danger. This type of sudden braking, as well as any type of driving on slippery roads, is exactly what your car’s ABS is designed to help with and while most people know their car is equipped with ABS and may know what that acronym means – but few know exactly what it is for and how it works.

HOW DO ANTI-LOCK BRAKES WORK

Simply put, an anti-lock braking system uses electronics to monitor the brakes and prevent the wheels from locking during braking. Wheels can lock when the brake is applied harder than the tire can handle and the wheel stops rotating, often causing the entire car to skid. A car’s anti-lock brakes will take effect when this happens and when they sense the wheel is about to lock, so anti-lock brakes reduce the risk of skidding when a driver brakes too abruptly, for example in a turn or an unexpected hazard on the road or when the brakes lose their grip on a slippery surface.

Anti-lock braking systems work through detection sensors installed on a car’s wheels. Each of these sensors is mounted in the wheel hub and takes readings of the rotational speed of each wheel. It looks for decelerations in the wheel that are out of the ordinary. Just before a wheel locks, it will undergo rapid deceleration. If nothing is done, the wheel would stop much faster than any car. It can take five seconds for a car to stop at 96.6 km/h (60 mph) under ideal conditions, but a locking wheel can stop rotating in less than a second.

These sensors assess whether one is about to lock when a driver brakes. The information is transmitted to the ABS electronic control unit, which determines which wheel is skidding and may lock. If a wheel begins to lock, the sensors communicate with the open hydraulic valves to slightly reduce the brake pressure and prevent the wheel from becoming completely stationary, thereby preventing the car from skidding. The cut-off corresponding to the wheel about to lock momentarily disengages from the brake master cylinder and the wheel is then controlled by the valves, which increase wheel locking, and the pumps, to reduce it, ultimately meaning the car can still be steered effectively. The result is that the tire slows at the same rate as the car, with the brakes keeping the tires very close to the point where they will begin to lock.

It’s as if the electronics are pumping the brake as a driver might do to avoid or prevent wheel lock-up. When the ABS system is active, you will feel a pulsation in the brake pedal; this comes from the rapid opening and closing of the valves. Some ABS systems can cycle up to 15 times per second, allowing them to achieve threshold braking, thus preventing loss of traction and the onset of a skid.

ADVANTAGES AND DISADVANTAGES OF ABS

ABS is particularly effective and now almost indispensable during emergency braking. It not only reduces the braking distance (assisted braking is much more effective than stopping via a completely locked wheel), it also allows the driver to maintain control of the vehicle during braking, which could help avoid serious problems.

Linked to this, ABS can help extend tire life. Tires that regularly skid on the road wear out much faster than those that do not, and as a result, anti-lock braking systems greatly help ensure that tires last as long as possible.

ABS also allows for safe driving in more challenging weather conditions like snow or during heavy rain. Although speeds should always be reduced in bad weather, ABS means there is less risk of tires losing their grip on the road and locking, making driving safer when weather conditions are not optimal, as the vehicle can still be steered effectively.

That said, however, ABS increases the braking distance on a slippery or snowy road, including on dirt paths. So, while it is good for steering in difficult weather, it is important to always consider the increased braking distance.

WHAT CAN GO WRONG: COMMON PROBLEMS WITH ANTI-LOCK BRAKE SYSTEMS

Since anti-lock brakes are so important, it is essential that you have an insight into what could go wrong with them. Helpfully, there is an ABS warning light on the dashboard that illuminates whenever there is a problem with your system.

Since the system is an electronic system, any wiring issues can cause problems. In particular, when an electrical wire is torn from the ABS sensor in one of the wheels, the correct measurements will not be received and the system will not function properly. The sensors are the most essential part of the system and, over time, they can become oxidized from prolonged and repeated exposure to moisture.

The efficient operation of the braking system is one of the essential conditions for safe driving. Therefore, keeping the brakes in good working order is a duty of every car owner: you must replace consumables on time, check for leaks in the lines, and remove air from the system if it has entered. Let’s explore the causes of air in the system. In this article, we tell you the correct order for bleeding brakes.

5 MAIN CAUSES OF AIR IN THE SYSTEM

HOW DO YOU KNOW WHEN YOUR BRAKES NEED BLEEDING

The presence of air is accompanied by characteristic signs. When pressing the pedal, you can feel that its resistance has significantly decreased. Sometimes, you need to press the pedal several times to get the brakes to work. With each press, the pedal becomes stiffer. Sometimes, braking starts when the pedal is pressed almost all the way down. Overall, your vehicle’s braking distance becomes considerably longer than usual.

HOW TO PREPARE YOUR CAR FOR BLEEDING

The sequence of steps for bleeding air from the brake lines varies depending on the vehicle’s make and model. It is also determined by the structure of the braking system and the presence of additional units and assemblies. Therefore, before starting the procedure, be sure to carefully read the vehicle’s manual. It should contain a detailed description of the bleeding process for your exact model. In some cases, if your car is equipped with many electronic systems, you won’t be able to do it without the help of a professional.

Prepare the brake bleeding tools and other necessary means and accessories.

You will need:

SPECIFICS OF THE BRAKE BLEEDING PROCEDURE ON DIFFERENT CAR MODELS

The order of steps depends on the following:

1. Presence of a brake proportioning valve on the rear axle. It is usually installed on utility vehicles and early-generation passenger cars. Under certain road conditions, it prevents brake fluid from being supplied to the rear wheels. Therefore, to properly bleed the brakes on these vehicles, do not unload the rear axle by lifting the car on a lift or jack.
2. Layout of the brake circuits. The procedure involves bleeding air from each brake mechanism. First, air is removed from one brake circuit, then – from the other. If the circuits are diagonal, start with the brake mechanism farthest from the master cylinder: most often, this is the right rear wheel. Then move to the front left, then the rear left, and finally, the front right.
   If the circuits are parallel and connect the rear and front wheels, the system should be bled in a circle. First, air is removed from the rear brake mechanism farthest from the master cylinder, then – from the other rear. After that, move to the front wheels.

3. Presence of the Anti-lock Braking System (ABS). This system prevents the wheels from locking completely during braking to avoid skidding. It can be found on most modern cars. It helps avoid loss of control during emergency braking or when trying to stop on a slippery surface. Its design includes a brake pressure modulator, and air must also be removed from it.

4. Hydraulic pump instead of the vacuum brake booster. You can see it on the BMW 7 Series (E32), Nissan Cedric Y32, Toyota Land Cruiser 105, Mitsubishi Pajero III, and other vehicles. In some cars, it is used in addition to the vacuum booster. In this case, you will need to turn on the pump to remove the air.
5. Additional features. If your car is equipped with, for example, an electronic stability control system, it is better to seek help from specialists at a garage to bleed the brake lines. You should also opt for professional service if the ABS units are located in different parts of the vehicle; because in this case, the procedure requires the use of a diagnostic scanner and is initiated using software. The Land Cruiser 200, BMW X5, and other cars are among such models.

HOW TO BLEED BRAKES ON A VEHICLE THAT HAS NO ABS

1. Unscrew the reservoir cap.
2. Fill the brake fluid up to the “Max” mark.
3. Pour fluid into the drain container.
4. Attach the hose to the brake bleeder screw and dip its other end into the drain container with fluid.
5. Ask an assistant to press the brake pedal several times in a row, then press it all the way down.
6. At the same time, unscrew the bleeder screw to allow the fluid to flow through the hose.
7. Tell your assistant to press the pedal all the way down.
8. Monitor the fluid coming out of the bleeder screw. There will be bubbles in it.
9. Tighten the bleeder screw. After that, your assistant can release the pedal.
10. Repeat the procedure 4 to 5 times for each brake mechanism.
11. Don’t forget to monitor the fluid level in the reservoir and top it up to “Max”.
12. While performing the work, ensure that the fluid does not get on the car body. It contains components that have a destructive effect on the paint. You must also prevent the substance from spilling onto the brake pads. If this happens, replace them.

HOW TO BLEED BRAKES ON CARS EQUIPPED WITH ABS

To bleed the brakes in vehicles where all ABS units are combined into a single module, proceed as follows:

1. Remove the ABS fuse.
2. Perform all the steps described above.
3. Reinstall the fuse.
4. Ensure that the dashboard warning light indicating an ABS malfunction is not lit.

HOW TO BLEED BRAKES IN CARS WITH A HYDRAULIC BRAKE BOOSTER PUMP

Proceed as follows:

1. Remove the ABS fuse from its socket.
2. Attach the hose to the bleeder screw. Dip its other end into the drain container filled with brake fluid.
3. Ask your assistant to press the pedal all the way down. In this case, there is no need to press it multiple times.
4. Tell your assistant to turn the ignition key to the corresponding position. This will activate the pump.
5. Wait for the pump to remove all the air from the system. In other words, until the fluid flowing from the bleeder screw has no bubbles.
6. Repeat the procedure for each of the wheel cylinders (brake calipers).
7. Monitor the fluid level in the reservoir. Top it up to the “Max” level before each cycle and also after completing the bleeding operation.
8. Ask your assistant to turn off the ignition.
9. Put the fuse back in place. Ensure that the dashboard warning light indicating an ABS malfunction is not lit.

HOW TO BLEED BRAKE LINES IF THERE’S NO ONE TO ASSIST

If you have no one to assist you, it is possible to perform the procedure yourself. There are several methods:

1. Bleeding is done in the same way as with an assistant, but you need to use a gas strut to hold the pedal down. For this, you can temporarily remove one from the hood or trunk lid. For convenience, you can purchase a special brake bleeding kit. It includes fittings, adapters, hoses, and a drain container. It is very convenient that the container is equipped with a powerful magnet, allowing it to be attached to any part of the car body and preventing it from tipping over and spilling the fluid.
2. Bleeding using a special vacuum pump. It is performed as follows: fill the reservoir with working fluid to the maximum level. Connect the pump hose to the bleeder screw of the wheel cylinder (brake caliper) you are working on. The fluid sucked out by the pump is collected in a special container, and the air is evacuated.
3. Bleeding by increasing pressure in the reservoir. You might need various devices for this: syringes, small manual compressors, and other tools. Their operating principle lies in supplying air or brake fluid into the reservoir under pressure. This circulates the fluid in the lines and replaces the process of pressing the pedal. The rest of the process is similar to a standard bleeding procedure: the brake fluid with air bubbles is drained through the hose attached to the bleeder screw of a wheel cylinder (brake caliper).

Conclusion

All malfunctions in the braking system, if any, must be eliminated immediately after they appear. There should be no air in the system. Therefore, as soon as you suspect air in your brakes, bleed them using our tips.

The filter that cleans diesel exhaust is essential, but can easily go wrong if you don’t know how it works.

If you drive a diesel car in 2021, there’s a good chance it’s equipped with a diesel particulate filter. You might not know what it is, how it works, or even when it’s doing its job. Diesel particulate filters have been installed on diesel-fueled cars for nearly two decades, and knowing how they are maintained can help keep your engine running cleanly and smoothly.

Here are all the details of what a particulate filter is and how to maintain and clean it.

WHAT IS THE PARTICULATE FILTER IN A CAR?

A diesel particulate filter (DPF) is a filter fitted to cars and it is designed to capture and store exhaust soot. Soot is a natural part of the combustion process, but larger chunks can be dangerous to an engine, so the filter removes that risk. While in the past only diesel cars were equipped with particulate filters, some gasoline car manufacturers have also started installing them on their vehicles. You can always tell a car that doesn’t have a DPF by the clouds of black smoke coming from the exhaust, especially when accelerating, for which diesel vehicles were notoriously known.

However, filters only have a limited capacity, meaning they will periodically need to remove the soot, which is called “regeneration” of the DPF.

If you haven’t heard of it, you might be wondering “when were diesel particulate filters introduced”? Particulate filters have been around for a while, since the introduction of Euro 5 exhaust emission legislation in 2009 to help reduce CO2 emissions from cars, they became effectively mandatory. All post-2009 cars compliant with the Euro 5 standard must be equipped with a DPF to reduce emissions.

HOW DOES THE DIESEL PARTICULATE FILTER WORK?

Soot is one of the byproducts of the combustion process. It is harmful both to the environment and to people and animals, so it’s the filter’s job to trap and remove diesel particles from the exhaust gases before they can be released into the atmosphere.

When you drive, the exhaust products pass through the walls of a series of channels that are blocked at different ends. Here, the soot particles are captured. The filter also removes the soot and it does so by exposing it to high temperatures. This burns the soot and leaves only a very fine ash residue. However, too much ash can accumulate in your filter and eventually cause blockages, which is why there is a regeneration process to clean the filter. Now it’s the turn of the blockages to be subjected to very high temperatures and then the harmless products that are produced can be released with the exhaust gases. No harm is caused to the environment or your car!

But it’s all about diesel, are gasoline engines also equipped with particulate filters? In the past, only diesel cars were equipped with particulate filters, but gasoline particulate filters (GPF) have also been developed for gasoline cars. A gasoline particulate filter works in much the same way, although there is no soot: the combustion products are still superheated, which removes harmful substances and leaves carbon dioxide. At the same time, nitrogen oxides and unwanted hydrocarbons are converted into carbon dioxide, water, and nitrogen, making the waste much less harmful. Once the filter has done its job, the exhaust gases pass into a three-way catalytic converter which ensures that the exhaust complies with the latest level of EU emission standards and that the number of harmful pollutants coming out of the exhaust is reduced. Thus, diesel and gasoline particulate filters work in much the same way and ensure that harmful products from the combustion process do not enter the environment.

WHAT IS DIESEL PARTICULATE FILTER REGENERATION?

The diesel particulate filter regeneration process is essential to ensure its proper functioning – it is essentially a cleaning of the particulate filter. Ensuring it is able to fully regenerate when full of soot is also the best way to maintain a DPF. When it is full, you will see a warning on the dashboard. There are two types of regeneration: passive and active.

Passive regeneration takes place when the car is driven at high speed on long journeys, for example on the highway. This happens here because the engine is running at higher RPMs. These longer, high-speed journeys allow the exhaust temperature to rise to a higher level and cleanly burn off the excess soot in the filter. To ensure this happens, drivers are often advised to regularly run their diesel vehicle for 30 to 50 minutes at sustained speed on a highway or A-road to help clean the filter.

The problem with this, however, is that not all drivers do this type of driving regularly. To solve this problem, manufacturers have equipped cars with an alternative form of regeneration, which is active regeneration.

Active regeneration involves the automatic injection of additional fuel, via commands from the vehicle’s ECU, when a filter reaches a predetermined limit (normally around 45 to 50% of its total capacity). This added fuel raises the exhaust temperature and burns the stored soot, as it would have on a long highway journey. However, the trip must be long enough to complete the process and you may encounter difficulties if the trip is too short, as the regeneration process may not finish completely. If this is the case, the warning light will continue to indicate that the filter is still partially blocked. Driving for about 10 minutes at speeds above 40 mph should be enough to complete a regeneration cycle and turn off the light.

Some signs let you know if an active regeneration is in progress.

They are:

WHAT IF BOTH TYPES OF REGENERATION ARE NOT WORKING?

If your warning light does not go out, turns red, or additional DPF lights come on, do not just ignore it. In addition to releasing a lot of dangerous gases into the air, it also risks damaging your engine. This can be very expensive to repair.

Some garages offered a forced regeneration service, which essentially involves cleaning blocked DPFs. This usually costs around £100 and, although it is not a 100% guaranteed solution, it generally succeeds in removing excess soot and allowing the DPF to function and regenerate automatically, which could prevent further problems later.

It is a failure of proper regeneration that is the cause of most diesel particulate filter problems: they become blocked, which increases exhaust emissions, chokes engine performance, and sometimes even puts the car into a restricted “limp home mode.”

Therefore, modern diesel car owners must be aware of the importance of maintaining their diesel particulate filter through their driving habits and practices.

WHAT CAUSES A DIESEL PARTICULATE FILTER BLOCKAGE?

Particulate filter faults are often caused by certain driving styles. Short, low-speed trips are the main cause of diesel particulate filter blockages. This is why car manufacturers often go so far as to recommend that drivers who only want to travel short distances in urban areas choose a gasoline car instead of a diesel and why so few “city cars” are diesels.

Poor maintenance can also lead to particulate filter problems. A diesel particulate filter on a poorly maintained car may fail sooner than a well-maintained one. How long particulate filters last is a tricky question, but they should last at least 100,000 miles. This could be halved if it is not properly maintained during service. This also includes using the right type of oil. Some oils contain additives that can actually block filters, so check what oil you are using and what oil is used when your car is serviced.

IS A PARTICULATE FILTER A LEGAL REQUIREMENT?

Yes, you must have one if your car was produced after 2009. Owners face fines if caught (up to £1,000 for cars and £2,500 for vans) and removing a DPF can also invalidate your car insurance.

DO I NEED A DIESEL PARTICULATE FILTER TO PASS THE MOT?

A diesel particulate filter check has been part of the MOT test since February 2014. If a filter has been removed, the car will fail its MOT. Removing the DPF will sometimes cause the warning light to come on – and that in itself is a MOT failure point: no dashboard warning lights should remain on during the test.

MY PARTICULATE FILTER IS BROKEN – HOW MUCH WILL A NEW FILTER COST?

Diesel particulate filters are very expensive. A new one directly from the manufacturer can cost between £1000 and £3500, which could potentially wipe out the cost savings associated with driving a diesel.

As cars age, the cost of replacing the DPF could be more than the value of the car – and it’s the older, higher-mileage cars that are most likely to need a new DPF.

There are aftermarket DPFs, but you must ensure they have the correct type approval and match the manufacturer’s specifications, otherwise they may not work properly and cost you more in repairs.

Help your engine breathe properly by checking your lambda sensor.

Somewhere hidden in the corners of your memory, the word lambda might ring a few bells. The symbol used to denote lambda, λ, might refresh your memory even more. Lambda is the term used to indicate the length of any wavelength in mathematics and physics and has long been part of the British school curriculum. But what does that have to do with your car?

A lambda sensor gets its name partly from its operation, measuring the output waveforms in different engine modes to see how much oxygen is coming out of your exhaust.

Essentially, this sensor measures the ratio of gasoline to air, the amount of oxygen in the exhaust gases. It does this to ensure that the amount of gasoline is accurately adjusted and that the catalytic converter can clean it.

There are many benefits to having a fully functional lambda sensor and it can cause a lot of problems if it malfunctions. So to make sure you’re on the right wavelength, here is our detailed guide on what a lambda sensor is, how it works, and how to detect if it’s faulty.

The lambda sensor is a small probe first developed by Volvo in the 1970s. The location of the lambda sensor is the same on all cars and it is located on the car’s exhaust, between the exhaust manifold and the catalytic converter. In principle, the lambda sensor is the same as an oxygen sensor. Newer cars might even have two lambda or O2 sensors and the second one will be located just behind the catalytic converter. Diesel cars have lambda sensors, just like gasoline cars.

The lambda sensor works with the catalytic converter and they “signal” the exhaust gases passing through the catalytic converter. The sensors measure the gasoline/air ratio to ensure that the amount of fuel injected exactly matches what is needed and that it can be cleaned by the catalytic converter. This air-fuel ratio is the stoichiometric ratio, or the lambda ratio (hence the sensor’s name).

SO, HOW DOES A LAMBDA SENSOR WORK?

The lambda sensor takes measurements of the amount of oxygen and adjusts the amount of fuel sent to the engine cylinders by optimizing the air and fuel mixture. This optimized air-fuel mixture means the engine can run at optimal performance. Since the lambda sensor is located before the catalytic converter, it can measure the amount of air and fuel in the unburned hydrocarbons after combustion. It will therefore be able to tell if there is too much air, meaning more fuel needs to be injected, or too many carbon atoms or harmful emissions, meaning more air is needed to react with the fuel. It will also ensure that the catalytic converter, which removes harmful and toxic byproducts from the combustion process when they are expelled from the car, is working properly.

The data, once collected, is sent to the Electronic Control Unit (ECU) and it controls the amount of gas released, thereby reducing polluting emissions.

There must always be the right amount of fuel reaction with the appropriate amount of air in the combustion process. If there is not as much air in the mixture as there should be, the engine is “rich” and there is an excess of unburned fuel. Unburned fuel creates pollution, which we try to avoid. On the other hand, when there is too much air in the fuel mixture, then it is “lean.” A lean fuel mixture tends to produce more nitrogen oxide pollutants, also toxic substances we should avoid. This can also lead to poor engine performance and potential engine damage.

Similarly, the lambda sensor affects fuel consumption as well as performance. Having too much fuel injected into the engine obviously means you will refuel more often. So it is extremely important to have the correct lambda sensor readings.

HOW DO I TEST MY LAMBDA SENSOR?

Testing a lambda sensor to see if it is still working couldn’t be easier.

You can check your lambda sensor with an exhaust tester or a four-gas emission analyzer. This is done in the same way as your emissions test and can also be done in a garage. The lambda value is calculated by examining changes in the exhaust gas composition over 60 seconds.

You can also use a multimeter. Connect it in parallel to the sensor’s signal line and set it to 1V or 2V. When you start your engine, a reading between 0.4 and 0.6 V should appear. Once the engine is at temperature, the reading should alternate between 0.1 and 0.9 V.

Finally, there are devices specifically designed to test your lambda sensor. As you would with a multimeter, connect the tester to the signal line, and when you reach the correct temperature, your reading will be displayed using the LED scale.

WHAT SHOULD A LAMBDA SENSOR READ?

It’s quite simple – it should read 1. If it’s less than 1 (λ <1), it means your air-fuel mixture is rich and if it's greater than 1 (λ> 1), it means the mixture is lean.

WHY DO LAMBDA SENSORS FAIL?

There are a number of lambda sensor failure issues. The heating element is a resistive material that resists the flow of electrons, thus producing heat and this is the most common cause of early failure. The resistance burns out by opening the circuit, meaning the sensor fails. Here, the sensor must be replaced. If the circuits connecting the electrical circuits linking the sensing electrodes to the PCM fail, this will also cause the sensor to malfunction. Contaminants from outside the sensor can also accumulate, either from the road or from the engine itself, blocking the air inputs and thus preventing assessment of the oxygen level in the exhaust gases.

SYMPTOMS OF A BAD LAMBDA SENSOR

If the lambda sensor is faulty, no data will be sent to the ECU, which will then use incorrect information. This will most likely increase fuel consumption and subsequently, polluting emissions. It could also mean that the catalytic converter clogs up and then needs to be replaced.

Symptoms

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The first indicator of a lambda sensor fault will be the check engine light on your dashboard – if this light is on, your lambda sensor may be faulty.

There are also performance issues that can indicate a faulty sensor: when starting, the car may be jerky and stutter; there might be abnormally high fuel consumption; the engine does not accelerate as well as usual; the amount of emissions has increased.

When should I replace the lambda sensor?

The lifespan of a lambda sensor is about 93,000 miles driven. However, this could be shorter depending on many factors that can damage it, mainly due to abnormalities from the engine. Exhaust leaks can also damage the sensor.

Many people want to know how to clean lambda sensors when they are, for example, covered in carbon and no longer working. However, this is a difficult process and should be left to a professional.

HOW LONG DO LAMBDA SENSORS LAST?

Due to their operation and the fact that they are located in an extremely hot and dirty environment, lambda sensors wear out over time. Several things can affect the lifespan of your sensor, but generally, it should last between 50,000 and 100,000 miles.

Early sensors did not have a heating element and they needed the exhaust temperature to reach a specific heat to function. Modern sensors are equipped with a heating element, which takes a lot of the pressure off the sensor and means they have a much longer lifespan.

If you are soon taking your car for an MOT test, be aware that a faulty lambda sensor will cause your car to fail. If you think it is faulty, get it sorted first. Driving without a lambda sensor is strongly discouraged as it ensures your car does not emit more CO2 than allowed by European legislation.

WHAT LAMBDA SENSOR DO I NEED?

There are hundreds of lambda sensors available, but you should always make sure to replace your sensor with one that exactly matches the same specifications as the previous one. You should always check what your manufacturer recommends because you will need the right option for your ECU.

HOW MUCH DOES A LAMBDA SENSOR REPLACEMENT COST?

A new lambda sensor costs on average between £100 and £200 (the spare part itself) and it takes the mechanic some time to replace it – about 1 to 1.5 hours. This means a total cost of around £250. You can try to replace it yourself, although it is a tedious process.

What goes in must come out – what happens to exhaust gases after combustion.

The combustion process is a wonderful thing. The process of taking only air and fuel and using compression or ignition to create mechanical power is one of the most important scientific discoveries of all time. What accompanies this power, however, are the exhaust gases that must be removed through the exhaust system, and that is precisely the job of the exhaust manifold. This makes it one of the most important parts of your engine, even though it’s just sitting there with gas moving inside.

This vital engine part is partly responsible for keeping the engine cool and allowing more combustion. Without it, all that science would be wasted. But what exactly is it? What is the temperature of exhaust manifolds? Why do exhaust manifold bolts break? Read on to discover everything you need to know about this important element of your car’s engine and how to identify some of the most common problems.

WHAT IS THE EXHAUST MANIFOLD AND WHY IS IT IMPORTANT?

A car’s exhaust manifold is used to direct exhaust gases from the engine cylinders to the exhaust pipe under the body. Once they leave the exhaust manifold, the gases pass through the emissions system and the car’s mufflers and exit through the tailpipe.

The manifold is a metal piece bolted to the side of the engine block on L-head engines and to the side of the cylinder head on I-head engines. Two, three, and four-cylinder engines have one exhaust manifold because there is only one bank of cylinders to extract exhaust gases from.

However, engines with a “V” configuration (V6, V8, and V12) have two manifolds, one for each bank. In some V-8 engines, each manifold is connected to a separate exhaust pipe, muffler, and tailpipe. On others, they are connected by a crossover pipe and exhaust through a shared muffler and tailpipe.

The exhaust valve opens to remove waste from the engine’s combustion process. When the engine’s intake valve opens and the piston descends, meaning the air-fuel mixture is drawn in through the intake valve, the exhaust valve is also slightly open. Without a manifold, all the combustion gases would rush out quickly, making the exhaust valve the path of least resistance for the airflow in the cylinder. With the air and fuel from the intake, the engine would suck cold air through the exhaust valve, exponentially increasing the combustion chamber temperature and quickly melting the exhaust valve, valve seat, and top of the piston. This phenomenon is known as “reversion” and is known to ruin engines. A manifold is key to preventing this.

The gases in the exhaust manifolds are very hot, which increases the pressure. This high pressure in the exhaust manifold forces the gas to “shoot” through the manifold and into the exhaust pipe. Because exhaust gases have mass, they also have inertia, creating a vacuum as they leave the manifold, in what is called “scavenging.” This sucks the remaining gases from the engine and leaves it as well-prepared as possible for the next combustion cycle, thus more efficient. Standard cast iron and “log”-type manifolds typically exhibit little of this power scavenging; the effect is usually most pronounced in tubular headers, which are designed to enhance scavenging.

WHAT ARE MANIFOLDS MADE OF?

Typically, manifolds are made of tubular steel, stainless steel, or iron. Stainless steel is the most expensive because it does not rust and has great longevity, but tubular steel provides good gas flow and is also commonly used.

You will find that most cars, however, have cast iron manifolds. They are cheap to produce compared to others, but they are heavier than steel and become brittle with age and prone to cracking, which we will come back to later.

While most manifolds are simply bare metal, in some cases, a ceramic coating can be applied to the manifold for insulation. This is expensive, and often an “exhaust wrap” is used instead, which is relatively cheap. This “exhaust wrap,” however, shortens the manifold’s lifespan.

Since exhaust manifolds are very hot, most of them are equipped with a metal heat shield to protect other components under the hood. This prevents any unnecessary melting of the engine!

If you are looking to replace your manifold, you can choose between those from your manufacturer, aftermarket alternatives, and even used manifolds salvaged from other cars. Just be sure to check what it is made of and its age first.

SYMPTOMS OF EXHAUST MANIFOLD PROBLEMS

Problems with your exhaust manifold can have serious consequences, such as reduced engine power, slow warm-up times, higher fuel consumption, and premature failure of the catalytic converter. To avoid this, it is important that you know the signs and symptoms that might indicate that your manifold is cracked, leaking, or has another issue.

AN EXCESSIVELY NOISY ENGINE

Engine noises are a good indication that you have a leaking exhaust manifold gasket. The manifold gasket creates a seal between the manifold and the cylinder head to prevent air from escaping, and a faulty manifold gasket sounds like a hissing or tapping. When you start the car cold, the sound will be at its loudest, and it will increase when you accelerate.

REDUCED POWER AND ACCELERATION

If your manifold gasket is leaking, you will notice that your car is not performing as it was or should be. The backpressure provided by the manifold ensures that the combustion process runs as well as possible. If the vacuum is not created, the process will not run as efficiently as it should. Your car will be slower and will not accelerate as quickly from a stop. Get this leak fixed, or the problem will only get worse. It should be noted, however, that a manifold is not the only reason for reduced power and acceleration.

REDUCED FUEL EFFICIENCY

Fuel efficiency goes hand in hand with performance, and as your car loses power, it will consume more gasoline. The car has to work harder and harder to maintain the same level of performance it would have without exhaust problems. While you might consider the cost of repairing any manifold issues, the cost of extra fuel will exceed it over time.

VISIBLE RUST ON THE MANIFOLD

Rust can appear on all metal parts, especially those exposed to air (rust is caused by metal oxidation). Since the manifold is metal, it can be prone to rust, especially if it is made of iron. The fact that the system is close to the ground where it is exposed to moisture and gritty conditions means it is particularly vulnerable. If the rust is severe enough to cause holes or cracks to appear in the manifold, you will start to hear a loud roaring engine noise or a hissing as gas escapes. This will certainly require professional attention and may potentially require replacing the manifold.

VISIBLE CRACKING

Besides possible noises and a drop in performance, the most obvious sign of a cracked manifold is, well, a visible crack on the surface of the manifold. To look for a crack, carefully examine the manifold, especially where it bolts to the engine and where the most heat will be. A large crack will be relatively easy to spot, but a smaller hairline fracture may be harder to locate. You may need to remove the manifold from the engine compartment to inspect the entire surface. This type of problem will let you know when to replace an exhaust manifold.

EXHAUST ODOR

Symptoms

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Exhaust odor is one of the most obvious symptoms of an exhaust manifold leak. Manifold cracks can also cause excessive exhaust odors, as some of the exhaust gases escape from the crack instead of the tailpipe end. You may not be able to notice this exhaust smell from inside the vehicle, but if you open the hood and the engine compartment stinks, especially around the manifold, it’s a good indicator. If you can smell an exhaust odor, it means the crack or leak must be quite severe, and this can be harmful to your health.

HOW TO REPLACE YOUR EXHAUST MANIFOLD AND GASKET

For a cracked exhaust manifold, you really have no other choice but to replace it. Trying to seal cracks is a bad idea, and using some sealant products could even damage the performance of the manifold itself if not done correctly.

Exhaust manifold gaskets can also be replaced to fix leaking issues, but they can also be repaired. A “blown” exhaust gasket can be replaced, or you can use a sealant to stop it from leaking, and a blowing exhaust manifold is something you can easily fix yourself.

The exhaust manifold can be found attached to the engine block. Consult your vehicle’s user manual to find the precise location of it in your vehicle. To replace the gasket or manifold, you will need to undo all the nuts and bolts that secure the manifold to the cylinder head. Sometimes the gasket may stick to the manifold; tap it with a hammer to loosen it. If any manifold studs are broken or damaged, remove them using locking pliers, two nuts and a wrench, or a stud extractor. Once the manifold is safely removed, carefully scrape all gasket mounting surfaces to remove dirt and pieces of the old gasket. Do not let particles fall into the manifold or cylinder head, as this will cause many problems later. This is a good opportunity to see if the manifold itself is cracked or damaged. Check that the surface is not warped.

If you are simply changing the gasket, place it in the position where the old gasket was, making sure it is facing the right way, with all holes aligned. On some engines, a gasket may be in two or three pieces, or inserts may be installed; make sure all parts are properly aligned. Finally, simply reverse these steps to reassemble your exhaust manifold. You should tighten the manifold nuts using a torque wrench and ensure you adjust them to the recommended setting in the car’s service manual. You should tighten them in order, starting from the center of the manifold and working outward toward the ends.

You might encounter problems here with the exhaust manifold bolts. It is important that you know how to remove exhaust manifold bolts without breaking them, and it can be a bit mysterious why exhaust manifold bolts break in the first place.

Since most manifolds are made of cast iron, when exposed to intense heat and then cooling, they regularly expand and contract. This expansion occurs naturally, and initially, the manifold and mounting bolts are in a state of “elastic deformation,” meaning they retain their original size and shape during these cycles and can be flexible, even when expansion/contraction puts pressure on the bolts.

Over time, however, expansion and contraction can subtly affect the manifold’s dimensions, and this means that increasingly larger tensile forces stretch the manifold beyond its “elastic deformation” point. This fractures the mounting bolts, leaving the manifold permanently deformed and dimensionally altered. This expansion and stretching of the manifold bolts over many service cycles eventually causes excessive stress on the bolt(s), stretching them beyond their capacity and causing them to fail. If this has happened, when you remove the bolts to replace the manifold, it may seem like you broke them, but this fracture occurred long before.

If you need to remove an exhaust manifold and the bolts (or even the manifold itself) are rusty and corroded, you will want to remove the bolts without breaking them. If you break them while removing them, it could risk parts falling into the engine itself and require much more work. It is best to leave this to the experts, but it can also be done using an acetylene torch to heat the studs that hold the bolts. This will allow you to remove them easily, but it certainly means you need to replace the manifold.

From bags to life and sorting our waste, recycling is great. So good in fact, even your engine recycles and reuses gas from the combustion process.

As climate change continues to shape the world around us, governments are taking action. For the ordinary car user, this often means problems. Car manufacturers are forced to reduce their exhaust emissions even more than they have over the past 20 years due to even stricter legislation. Diesel and gasoline manufacturers are doing everything they can to catch up with electric and hybrid cars and comply with new emission standards.

Exhaust Gas Recirculation (EGR) systems are one of the ways conventional fuel engines attempt to achieve this. The ingenious system helps reduce the amount of nitrous oxide – one of the most harmful byproducts of the combustion process – that comes out of your car’s exhaust. On gasoline engines, the system also reduces fuel consumption when the engine is running at partial load. But what is an EGR system, how does an EGR valve work, and what are common EGR problems? If you’re exhausted from searching for answers to these questions, look no further!

WHAT IS THE EXHAUST GAS RECIRCULATION SYSTEM?

Simply put, the Exhaust Gas Recirculation (EGR) system reduces NOx emissions from internal combustion engines. The system is composed of an EGR valve, a temperature sensor, and a control unit and it is connected to both the ECU and the engine’s intake/exhaust manifolds.

The main goal is to reduce these NOx (nitrous oxide) emissions and it does this by recycling exhaust gases into the combustion chamber, where they cool the combustion. The gases that have already been used in the combustion do not participate in the next combustion process, but they still help reduce NOx and also the temperature of the chamber itself.

Part of the reason for wanting to keep the chamber temperature low is that if the combustion temperature is high, it can lead to engine overheating and also more nitrogen oxide in the engine’s combustion chamber. The combustion temperature in the combustion chamber is reduced by recirculating some of the exhaust emissions into the fresh intake air and the lower combustion temperature results in less nitrogen oxide and an engine less likely to overheat.

HOW DOES THE SYSTEM WORK AND WHY DO YOU NEED IT?

As part of the combustion process, air enters the combustion chamber through the intake manifold and mixes with fuel. When it is compressed or ignited (depending on the system), the pressure forces the piston down to power the engine and the exhaust gases exit through the exhaust manifold. If an engine is running at full load, that is, it is operating at its greatest capacity, during intense acceleration for example, this process works perfectly and all the oxygen atoms in the air that are drawn into the intake manifold are used in the combustion process.

What normally happens is that an engine only runs at partial load. When you are simply driving on the road, idling, or slowly looking for a parking space, the engine is not running at full capacity, which we call a partial load. This becomes a problem regarding emissions. Because less fuel is injected (because the engine is not forced to work as hard), not all oxygen atoms are used in the combustion process. The remaining atoms combine with nitrogen (which makes up 70% of the air entering through the intake manifold) to form NOx (nitrous oxide). Unfortunately, this is a toxic air pollutant and it is exactly what the new government legislation aims to prevent. This is where the EGR comes into play.

In the final exhaust phase of the 4-stroke combustion process, when the exhaust gases leave the cylinder, the exhaust gases are partially rerouted inward and pumped back into the combustion chamber. Before getting there, there is an exhaust gas recirculation valve. The location of the egr valve depends on your car’s system, but it is always before the intake manifold so it can regulate the amount of recycled gas.

The gas already used in the combustion combines with the fresh air also entering the chamber and the gas that then enters the chamber is a combination of gas already used in the combustion process and fresh air. The valve regulates the amount of this gas allowed.

By working with the ECU, the sensors determine the load on the engine, i.e., the amount of power required from the engine, and the amount of recycled exhaust gas is calculated accordingly.

The lower the load, the more exhaust gases are recycled because there will be less fuel injected into the cylinder and thus more harmful NOx byproducts.

If the load is higher, more fresh air and oxygen are allowed and thus less exhaust gas is recycled. Since the already used gas is inert (it does not react), there is no risk of it reacting with oxygen to produce more emissions.

The gas temperature also impacts the combustion process and offers another advantage. Since the exhaust gases are hot, it decreases the time needed for the gas in the cylinder to reach the temperature required to exert pressure on the piston and thus eliminates “ignition delay.” In short, it makes the engine more efficient and faster, providing more controlled combustion.

As mentioned above, this process also decreases the temperature of the combustion process. The compression gases raise the temperature needed to apply pressure to the piston. But the inert gases absorb this temperature because they are at a lower temperature than the compressed gas. The heat is absorbed by the recycled gases and means there are fewer NOx byproducts and a lower risk of engine overheating.

WHAT ARE THE COMMON EGR PROBLEMS?

The EGR is used continuously with the engine and the system is therefore subjected to very high loads, which can cause problems, especially on high-mileage vehicles. Since the valve is the most important part of the system here, most problems are associated with it.

It is quite obvious if there is a problem with your EGR valve because your car will experience bad EGR valve symptoms like rough idling and stuttering during acceleration. Your fuel economy will also decrease due to a faulty EGR valve and you may see a check engine light on the dashboard followed by a code readable in your car’s OBD-II or newer computer.

Causes

The likely causes of these symptoms will be a stuck EGR valve. A buildup of deposits in the EGR valve over a period of time causes the valve to let less or no recycled gas through, meaning your car’s performance will start to suffer (the ECU will assume the correct amount of gas for combustion is in there, as it assumes the valve is working). This happens especially often with a diesel EGR valve. This buildup is part of the vehicle’s ordinary operation and can be fixed by either cleaning or replacing the valve.

Cleaning the EGR valve is not as tricky as you might think and you can certainly do it yourself. Once you have located and removed your EGR valve (the location varies from vehicle to vehicle, so check your user manual), shake it gently. If you hear something moving back and forth inside, it’s the diaphragm – meaning there’s a good chance your EGR valve is still in good condition and just needs to be cleaned to return to its normal operation. If you don’t hear anything, your EGR valve may be stuck. This is not a definitive test, but it’s a good starting point.

If you have a newer EGR valve, it will likely be electronic and therefore have a wiring harness connected. In this case, it is important to avoid putting corrosive cleaners on the wiring and connectors and of course, the engine must also be off. You will also need reliable eye protection and chemical-resistant gloves.

CLEANING AN EGR VALVE

First remove the vacuum line, which is the rubber line connected to your EGR valve. If it is brittle, broken, frayed, damaged in any way, or looks less than perfect, replace it. Vacuum issues are the cause of all sorts of engine problems, including a faulty EGR valve.

Then disconnect the electrical harness and unlock the EGR valve. If it doesn’t come right away when you have removed the nuts or bolts, you can loosen it by giving it a tap with wood or a small hammer.

Then remove the gasket and check that it is in good condition and not torn, frayed, or disintegrated. If it doesn’t look so fresh, you can install a new one at the same time.

Cleaning the entire valve assembly is a two-step process. First, soak the valve itself in a bowl filled with carburetor cleaner. Carburetor cleaner smells horrible and is unpleasant, so soak it outside or in a very well-ventilated area. Let it soak overnight if you can. If that’s not possible, move on to the next step.

Once you have let your EGR valve soak in the cleaner overnight (if possible), you need to clean its passages, openings, and surfaces with a small brush. Toothbrushes and pipe cleaners soaked in the same carburetor cleaner you were using before are perfect for this. Be sure to use your eye protection and gloves at this stage to avoid injury. You want to clean as much of the valve as you can and get into as many nooks and crannies as possible – the more black sediment you remove, the better your chances of solving the problem.

Once it is clean and free of crust, you can reinstall your clean EGR valve. Remember to reattach your vacuum hose and electrical connections if necessary. If you are still experiencing problems once you have cleaned the valve, you may need to replace it.

UNCHECKED CO2 AND OTHER GASES CAN HARM THE ENVIRONMENT AND YOUR WALLET

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An air suspension upgrade can improve your car’s comfort.

Whether it’s speed bumps in a residential cul-de-sac, low curbs on driveways, or even potholes or unintended bumps on the road, it’s sad to say that roads in the UK don’t really favor heavy-load-bearing or high-performance sports vehicles. There have surely been times when you’ve wanted to raise your truck’s or car’s suspension to help it clear an obstacle more easily. Similarly, sometimes when there’s nothing in the back of your van, you’re sitting quite high and you can feel yourself going much slower than usual. While normal suspension systems that revolve around coils and springs are comfortable and maintain good vehicle handling, they don’t offer you the possibility to raise or lower your vehicle. Enter air suspension.

Air suspension, or air-ride, has been around for a long time, and replacement kits first appeared for sale to be fitted to cars as early as 1920. In addition to providing driver comfort, it was used from the start as self-leveling suspension for heavy loads. People even used it to help smuggle illegal moonshine! That’s why, even today, many new trucks and trailers are equipped with air suspension systems, and there is a multitude of replacement kits that can be fitted later.

Air Lift is one of the best-known companies for replacement air suspension, and it has been around since 1949. Although we tend to associate air-ride as being more focused on comfort than performance, it was extremely popular in dragster and NASCAR racing in the 50s and 60s.

So, what is this air suspension, why do people want it, and what are the advantages and disadvantages of using air suspension?

WHAT IS AIR SUSPENSION AND HOW DOES AIR SUSPENSION WORK?

Conventional shock and spring suspension systems that feature steel components provide a vehicle with great handling and fantastic performance at all levels. Air suspension, however, replaces these components with robust rubber airbags that can be inflated using an onboard or external air compressor. This allows the vehicle to raise itself or lower itself depending on the inflation level of the airbag and can make a car much more comfortable to drive or give it a better appearance. Does air suspension affect performance? Yes – but not necessarily in a bad way. Modern kits also feature elements such as adjustable camber mounts and adjustable damping, meaning you can have the best of both worlds.

It’s important to note that there are two different types of air suspension: “semi” air suspension and “full” air suspension.

“Semi-air suspension” supports the existing suspension of a car. This is often found on heavy goods vehicles or trucks. An air spring is installed between the chassis and the rear axle, which increases the vehicle’s ride height and generates greater spring travel. In this way, semi-air suspension helps increase the level of comfort and stability when you are traveling in your vehicle.

If you have suspension issues, full air suspension could be a fully automatic and adjustable solution. The conventional suspension system is completely replaced by a full air suspension system that filters out road surface irregularities, making the ride much more comfortable.

So, ultimately, the only major difference between conventional and air suspension systems is that instead of the car sitting on a coil spring, it is sitting on a rubber bellows of compressed air. As the bags are not pre-inflated, they are powered by an air tank and an electric air compressor, with the car needing to be lifted and lowered simply by inflating and deflating the bag.

WHAT ARE THE KEY COMPONENTS OF AN AIR SUSPENSION SYSTEM?

AIR SPRINGS (BAGS)

These are solid rubber bases that replace the coil spring of a conventional setup. They come in two main styles: the coilover configuration or the conventional style. In the coilover configuration, the bag has a hole in the middle allowing the shock absorber to pass through it. In the conventional style, the bag is completely independent of the shock absorber.

Modern airbags are not like a balloon filled with air that we might imagine. They are solid and durable and are designed in such a way that they only expand and contract from top to bottom. At full inflation, they can have an air pressure of 100 psi.

SHOCK ABSORBER

If you have a suspension design where the spring is mounted separately from the shock absorber, the same shock absorber that you would have used with your conventional coil spring can be used. Fortunately these days, with the rise in popularity of airbags in the tuning scene, there are now coilover-style kits for a wide range of cars, offering a matched shock and airbag combo. These kits not only simplify installation, but they improve handling and ride. Many of them feature shock absorbers with height-adjustable platforms for the bags, adjustable damping, and even adjustable camber top mounts.

COMPRESSOR

Air doesn’t just magically enter the airbags. That’s what the compressor does. All air suspension kits require at least one compressor, and you’ll generally find that the one supplied is quite small and compact; they often fit neatly in the car’s trunk. They often run on a 12-volt power supply and therefore won’t drain your battery. The big issue is, however, that they are often very noisy.

AIR TANK

That noise from the compressor is what makes the air tank necessary. You could have air-ride without it, but the pump would have to run far too often and it would take too long to lift the car unless the pump was gigantic. An air tank is used as the main supply for the airbags, and the air compressor simply serves to keep the tank above the minimum pressure. Depending on the size, air tanks allow the suspension to be lifted at an acceptable speed without the compressor needing to kick in. This also needs to be stored in the trunk of many cars. You just have to decide what matters most to you; more trunk space or a larger tank.

ADVANTAGES

IMPROVED FUEL ECONOMY

The higher your suspension is, the higher the wind resistance of the truck and trailer, meaning your fuel economy is going to be worse.

Advanced air suspension systems can adjust the ride height based on the load weight and the type of journey you are making. For long highway trips with light loads that don’t compress the suspension as much as heavy loads, the suspension can be set lower to maximize your fuel economy. For heavy loads, the suspension can be made as firm as needed and the vehicle remains lower to the ground due to the heavy load. In both situations, the vehicle remains low and allows you to save fuel. In a conventional suspension system, if the load was light, the vehicle’s suspension, which is designed for heavy loads, would remain stiff and your fuel economy would be much worse due to the resistance.

MORE ENVIRONMENTALLY FRIENDLY THANKS TO REDUCED CO2 EMISSIONS

Due to this decrease in fuel consumption and the smooth ride, it automatically means you use less fuel, journeys are faster and shorter, and consequently, it’s much better for the environment. That’s something we can all be happy about!

REDUCED VIBRATION

Better for your cargo and better for your back on those long journeys, air-ride reduces vibrations from the truck or car. Back pain isn’t just something that comes with age; Long-distance heavy goods vehicle drivers can experience it if they are in a seated position for a long time. Vibrations also cause fatigue and discomfort, meaning a happier, fresher, and ultimately safer driver.

Similarly, the cargo carried by the truck is less likely to be damaged or shift in the back of the van or truck as well (although load packaging and restraint methods these days are very good anyway).

Alongside this, a trailer can be used for more types of loads when the suspension setup is flexible. Fragile loads such as glass are less likely to be damaged, and loads with difficult weight distribution can be leveled.

IMPROVED TYRE WEAR AND HANDLING

Less vibration and better load distribution through leveling improve tire wear. Some air suspensions can even lift unused axles, thereby prolonging the life of those tires.

Suspension is also a major factor in how a vehicle behaves. Better suspension could mean less likelihood of a rollover event. If the vehicle is higher off the ground, it is much more difficult to handle, and this can be a problem for vans or trucks with a rigid suspension system when they are not carrying a load.

EASY INSTALLATION

The advantage of these systems is that they are very easy to install. 5 years ago, it might have been a bit different, but nowadays, there are various direct replacement kits for a large number of popular cars. While fitting a full air suspension system to a car remains a job for professionals, for most of us, fitting a semi-air suspension is no more difficult than fitting a set of coilovers and shouldn’t take more than a day to do. These “plug-and-play” semi-air suspension kits are also relatively inexpensive. Where to install the air suspension isn’t much of a problem because these kits are designed to fit current suspension systems, provided there is trunk space for the tank and compressor.

DISADVANTAGES

This isn’t to say, however, that everything is perfect for air suspension systems, and there are a few disadvantages.

Some truck drivers still argue that traditional leaf springs in an articulated truck can offer a better ride, regardless of the load. This could be partly due to the fact that air suspension can be about 50 kg heavier than leaf spring suspension. This extra weight could actually counteract the “better” handling offered by the lowered vehicle and make driving more difficult.

Since it weighs so much more, it might be possible to install other aerodynamic devices such as trailer skirts and cab side fairings to achieve the same fuel economy gains instead.

Leaf spring suspension is also much more durable and typically doesn’t require much maintenance for the first 5 to 7 years, after which it will need to be tightened. On the other hand, with air suspension, cars need to be serviced more frequently – up to 3 times the cost over the first ten years. Air suspension can leak, and you will need to keep a spare air line and other parts. Air suspension also needs to be tested more frequently, which takes time.

Although leaks are rare, finding them can be a bit frustrating. You will also lose some of your boot space. You need a decent-sized tank to prevent the noisy compressor from kicking in when you lift the car. Height changes are not as fast as with hydraulics.

Common air suspension problems can also be that the air suspension is inactive due to a leak or that the control unit is broken. The compressor could also fail, or the air tank could lose pressure. These all need to be repaired or replaced, which could cost you more due to repair costs at a garage.

THE VERDICT

So, what is it really like to have air suspension and use it daily? Better than most people might expect. A good kit, properly set up, will perform much better than conventional suspension in vans or trucks. For your average passenger vehicle, it might not be worth it, as regular suspension will serve you just fine. That said, people have happily drifted and set respectable lap times on air-ride setups, so if you have a particularly low-slung car, like a Porsche Carrera or almost any Mercedes S or E, it could be an option for you.

You will of course lose a bit of trunk space to the compressor and air tank, but no more than with a subwoofer box or a nitrous bottle, and there is very little weight disadvantage to adding the air-ride kit either.

Don’t be mistaken, however: air-ride doesn’t offer the instant height jumps that hydraulic systems do (you won’t be bouncing like a lowrider), but it really only takes a few seconds and with the right-sized tank can be done silently too. If you’re wondering if air suspension is reliable, rest assured that it is, and countless people have these systems on daily-driven cars without any problems.

Modern automobiles often prioritize comfort and luxury alongside speed and performance. People tend to think that heated seats or cruise control systems add comfort to a journey, but the most important factor in ensuring every trip is as smooth as possible? Suspension. A car’s suspension system is undoubtedly the most important factor for having comfortable and stable performance and allowing the driver to truly control their car. But what is the purpose of the system, besides comfort, and how does it work?

THE FUNCTION OF SUSPENSION SYSTEMS

The main job of a car suspension system is to ensure that there is maximum friction between the tires and the road surface, to ensure steering stability with good handling and to ensure passenger comfort. It is intended to absorb vibrations, gravity, and impact forces from the road.

If every road were completely flat, without bumps, potholes, or irregularities, suspension systems would not be necessary. But unfortunately, this is not the case anywhere in the world. Even freshly paved streets have tiny imperfections that can interfere with a car’s wheels and its operation. These imperfections exert a force on the car, pushing it upward. The magnitude of the force, of course, depends on the size of the imperfection that was hit. In any case, the car’s wheel experiences vertical acceleration when it passes over an imperfection. It is the job of the suspension system to handle these upward forces and ensure that the wheels remain on the road at all times.

If it works correctly and the wheels are constantly in contact with the road surface, then there is maximum friction and the risk of rolling or overturning the car is minimized and this helps ensure that power is transmitted to the wheels, where it is most needed. The tires absorb all shocks and vibrations, as well as other road imperfections, and in conjunction with the car’s shock absorber mechanism being part of the suspension, the effects of these shock forces can be effectively dampened. It is technically the spring mechanism of modern suspension systems that pushes the tires into the ground so that we have maximum friction and the best possible ride. Thus, when a tire hits a bump or is forced upward because of something on the road,

COMPONENTS OF A SUSPENSION SYSTEM

Before looking at the different types of suspension and how they work, it is important to have a basic understanding of the key elements of almost all suspension systems.

The key components of a suspension system are the springs, the shock absorbers, and the anti-roll bars. To bring it back to basics, the springs absorb the force of the impact, the shock absorbers then work to dissipate this energy, and the stabilizer or anti-roll bars are used alongside the shock absorbers to give the automobile extra stability when driving. An anti-roll bar is a metal rod that spans the entire axle and connects each side of the suspension together.

SPRINGS

There are, of course, several types of springs, shock absorbers, or stabilizer bars. Leaf springs are one of the oldest forms of suspension springs. These springs are essentially several layers of metal bound together to act as a single thin, arc-shaped unit. They are attached to the axle and when the car hits a bump or road irregularity, the layers compress to absorb the shock. Although these are much less common for cars nowadays, they can still be found on heavy vehicles and trucks in the United States.

Coil springs are the most common spring component of a suspension system. A coil spring is a robust torsion bar wound around an axis. The stiffness of the spring affects the reaction of the sprung mass (everything located above the springs and thus supported by the springs) when the car is driven. If there is very little tension in the spring, it is “softly sprung,” it’s probably a very smooth ride. Luxury cars, for example, are often softly sprung. However, they can be prone to diving and squatting during braking and acceleration and have more body roll or sway in corners. Tightly sprung cars, on the other hand, give less when hitting bumps, which can be uncomfortable, but minimize body movements so they can take corners aggressively, ideal for a sports car.

A common feature of European vehicles is a system involving a suspension arm or an “A” control arm. This one consists of a torsion bar attached to a “triangular” arm (so called because it has the shape of the V-shaped “wishbone” from a turkey’s neck) and to the vehicle’s chassis. The wishbone acts as a lever that moves perpendicularly to the torsion bar; when the wheel hits a bump, the vertical movements are transferred to the wishbone or control arm, then through lever action to the torsion bar. The torsion bar then twists along its axis to provide the spring force.

SHOCK ABSORBERS

When the springs absorb the force and energy from the uneven road surfaces, this energy must dissipate in one way or another. That is the job of the shock absorbers. Shock absorbers are therefore a type of damper. They slow down and reduce the amplitude of vibratory motion by converting kinetic energy into thermal energy to be dissipated by the hydraulic fluid. Shock absorbers are speed-sensitive; the faster the suspension moves, the more resistance the shock absorber provides. They can adapt to road conditions and control all unwanted movements, including bounce, sway, brake dive, and acceleration squat.

Struts are a more advanced form of shock absorber and are essentially a shock absorber mounted inside a coil spring. It works simultaneously as a damper like a shock absorber and structurally supports the vehicle’s suspension – they do more than shock absorbers because they support the vehicle’s weight to some extent. Struts are very common in the front suspension of front-wheel-drive vehicles.

TYPES OF SUSPENSION

Different combinations of spring systems and shock absorbers can be found in different vehicles and the type of suspension used can even vary within vehicles – the front suspension system is likely to differ from the rear suspension system.

A suspension system can be dependent and independent. In a dependent suspension system, a rigid axle links two wheels together, while in an independent system, the wheels are allowed to move independently and are not connected to each other. Older cars tended to favor dependent suspension systems, often in conjunction with leaf springs, but more modern cars prefer independent suspension systems, especially for the front suspension. Dependent systems are robust and simple, but since there is no camber adjustment in corners, there is a risk of the wheels lifting off the road surface. As for independent suspension systems, shock loads from the road surface are isolated to the side where they are encountered, which is extremely advantageous. Of course,

Often, the front and rear suspensions of cars will be different. Front suspension systems must be integrated with the steering and can therefore be quite complex and they are also the first to come into contact with foreign objects or uneven surfaces on the road. Rear suspension systems can often be simple because steering does not need to be taken into account. This means they are often dependent systems (see below for an explanation), based on a leaf spring or a coil spring. If all our wheels have individually mounted suspension, the car can be considered to have four-wheel independent suspension.

DOUBLE WISHBONE SUSPENSION

Double wishbone suspension consists of two triangular-shaped arms (A-shaped or V-shaped) positioned one on top of the other. They are hinged at the top and bottom of the vehicle’s steering knuckle to ensure the vehicle’s steering and balance the steering wheel. Shock absorbers are often attached to each control arm and this type of suspension gives more control over the wheel’s camber angle to minimize roll and sway and provide a more consistent steering feel. These are popular on the front wheels of larger cars, which can be heavier and prone to rolling or swaying in corners. Although it is lightweight and has many advantages, it is also more expensive than solid beam (dependent) suspension systems.

SHORT/LONG ARM SUSPENSION (SLA)

Short/long arm suspension is a modification of double wishbone suspension that can be used on both the front and rear wheels of motor vehicles. In double wishbone suspension, both arms are of equal length. In a short/long arm (SLA) suspension, the two arms are of unequal length; the upper arm is shorter than the lower arm. This design allows for camber control and limits tire edge wear during cornering. The length of the upper arm is shortened so that, in corners, with centrifugal force tending to roll the vehicle and put the tires on their edges, this suspension system acts to bring the contact patch back to the center of the tire for both wheels. This effect occurs up to full jump, making it an ideal suspension for performance vehicles.

MACPHERSON STRUT SUSPENSION

This system includes a single control arm in a strut assembly that allows the tire and wheel to move up and down. This reduces unsprung mass and increases ride comfort. It is small, relatively inexpensive, and not too complicated, meaning it is a popular strut choice. On some of the same vehicles, a strut is also used in the rear suspension system. It is similar to the front strut but does not have an anti-friction bearing at the top because it is on a non-steering wheel.

ADJUSTABLE AND HYDRAULIC SUSPENSION

Besides all the basic types of suspension systems that manufacturers offer as standard, many drivers opt for adjustable suspension systems that they can install, adjust, and maintain themselves. These can also be provided by some manufacturers as standard in new cars. Some suspensions allow adjustment by the driver or automatically by the car itself and these can help deal with certain conditions. Indeed, a car with adjustable suspension can take on the function of two or more slightly different suspensions, depending on the situation.

Two main settings can be adjusted with adjustable suspension systems: ride height and roll stiffness. High-end cars can sometimes be equipped with the ability to raise and lower their body depending on the situation. The Tesla Model S is a good example as it automatically lifts when driven into entrances like parking lots or driveways. Some SUVs can be set to a lower suspension height on smooth roads, for more stability and economy, or higher in off-road driving, for increased ground clearance.

Ride height adjustment normally uses airbags integrated into the springs; changes in the amount of lift correspond to any change in air pressure. Other manufacturers use hydraulic systems to accomplish the same thing, with pumps providing hydraulic pressure to help lift the vehicle.

Some vehicles offer active suspensions that automatically stiffen the ride when a driver maneuvers at high speed; they do this using a pneumatic (air) or hydraulic (fluid) reservoir with variable pressure. Roll stiffness adjustment is built into aftermarket systems that feature adjustable spring rates and/or shock absorber performance. Most of the time, making adjustments like these means physically getting under the car and changing something manually, most often a dial on the shock absorber that changes the shock absorber’s tendency to dampen movement. Systems that can be adjusted from inside the car are much less common.

Dedicated race cars go even further than these two systems, allowing adjustment of almost every aspect of the suspension. A qualified race mechanic can tailor a race car to each individual track.

Nowadays, adjustable height suspension is increasingly offered by the manufacturer, as concerns about fuel economy increase. When cars are lower, they become more aerodynamic and thus more fuel-efficient. The other types of adjustable suspensions listed above are found mainly in aftermarket systems (to be added after the manufacturing process), especially in adjustable shock absorbers and “coilovers” (systems comprising a coil spring and an associated adjustable shock absorber or strut). But in all cases, the intention of a suspension adjustment is the same: to incorporate a change to help adapt to different needs or conditions.