Car overheats frequently.
by Visitor in Charlotte, NC on August 11, 2011
First confirm that the engine IS actually overheating - steam, no heat to the interior etc. Sometimes a temperature sensor will fail and give a misleading 'overheat' reading on gauge. For that matter sometimes the gauge can fail and give the same misleading reading. Check that the cooling fan comes on when the engine temperature starts to rise above 'normal'. If not check (in order) fan fuse, fan relay, fan sensor, fan. Real overheating is caused by a lack of coolant AND/OR lack of coolant flow. Modern cooling systems are 'closed'. In other words there should be little or no loss of coolant. If the level is significantly low you have a leak....either external or internal. With the coolant topped up to the correct level and the radiator cap on, run the engine and look for visible leaks...hoses, valves, radiator etc. Internal leaks, eg. head gasket will usually be accompanied by white exhaust smoke (steam), hard starting, rough running and bubbles in the expansion tank. Sometimes, though NOT always, you will find the engine oil has a milky look and/or engine oil will be mixed in with the coolant.