Symptoms
- The engine temperature gauge indicates a temperature higher or lower than normal. If the vehicle does not have a temperature gauge, it will have a “red” temperature warning light, meaning the engine is already overheating and must be stopped immediately.
- If the gauge is faulty or goes unnoticed, an overheating engine will cause the coolant to boil, producing steam, the radiator/reservoir will overflow, and in critical stages, the engine will start knocking, lose power, and finally seize.
- If the engine runs cold, the fuel mixture will be rich, leading to poor fuel economy, the heater will not work well, and the temperature gauge will indicate colder than normal. All engines are designed to expand to a predetermined point as they heat up. Maintaining the correct operating temperature is essential for proper piston ring sealing.
Effects on the Engine
Running too cold leads to overheating. The effects of running too cold occur over time and are correctable, while overheating is always catastrophic if not addressed quickly. A few minutes of severe overheating and the engine will be destroyed.
Mild overheating typically results in a blown head gasket, which is an expensive repair. Severe overheating will cause the pistons to expand faster than the cylinder block, leading to seizure in the cylinder bores for which there is no repair.
Procedures and Protocol
Due to the wide range of possibilities for overheating as the cause of code P2181, the following strategy will be used. The diagnostic flow will be used from the perspective of an automotive technician. It will start from the most commonly encountered to the least.
Warning: Never open a radiator cap unless the engine is barely warm or cold. The cooling system is under pressure, and the common temperature is 195 degrees, while an overheating engine can exceed 280 degrees. Third-degree burns will certainly occur.
Diagnostic Steps
and Possible Solutions
Tools Used to Diagnose Overheating Issues:
- Temperature scan tool
- Voltmeter
- Set of alligator clip jumper wires
- Scan tool to clear codes
- Cooling system pressure tester
- Service manual
Engine Too Cold:
- Replace the thermostat.
Engine Overheating:
- Plug the code scanner into the OBD port and turn on the key. Check for any other codes. A coolant temperature sensor code will cause the radiator fans to malfunction.
With the engine cold, remove the radiator cap and check the coolant level. Use the pressure tester to check for leaks in the system. This includes the radiator, hoses, block, intake, and heater core. - If the engine temperature is normal while driving but overheats when idling, the radiator fan is malfunctioning.
- Check the serpentine belt tension for proper tightness. Faulty belt tensioners are common and allow belt slippage. Check for leaks around the water pump. For those driven by the timing belt, coolant leaks from the bottom of the belt cover. If the water pump is exposed, check if the pulley wobbles, indicating a worn water pump bearing.
Check that an engine-driven fan does not wobble and does not leak around the fan clutch. Spin the fan by hand. A good fan clutch offers some resistance. An unusually slow fan with the engine running indicates a faulty fan clutch. - Check the coolant level sensor on the side of the radiator by referring to the service manual.
- If the vehicle has a radiator cap, leave it off, start the engine, and let it warm up. Monitor the engine temperature with the scan tool, and when the temperature approaches 190 degrees, watch for coolant flow from the inner cores of the radiator. If no flow is detected above 195 degrees, replace the cap and stop the engine. The thermostat is faulty.
- If the radiator starts to flow, replace the cap and let the engine reach 205 degrees before shutting it off. If the electric fans do not turn on, shut off the engine.
- Check the engine fan fuse and relays in the driver’s side fender relay and fuse box. Their location is indicated on the underside of the cover.
- Check the fan operation by disconnecting the wiring pigtail. Use a jumper wire from the ground terminal to a good ground and from the power terminal to the battery. If the fan does not run, replace it. If it runs, check the wiring at the fuse and coolant temperature sensor for loose connections, pushed-out connector pins, or burnt wiring.
- Check for a blown head gasket.