What would make your car overheat if the thermostat is good?

Answer 1

If your car has cooling fans, make sure they are working correctly. Make sure the radiator isn't leaking and not restricted either on the inside or in front on the outside. Caution: Always disconnect the negative battery cable before putting you hands into a vehicles engine compartment. Caution: When the engine is hot be very careful not to touch hot engine parts. If your not sure what your doing get help from a pro. First when the engine is cold check the radiator and make sure it is topped off with coolant. Reply: This could be caused from a number of reasons and it is helpful to give more information about the car like make model and year. Let me explain there are at least two ways of cooling the radiator. Some cars have an electric fan that is controlled by a thermostatic switch normally located near the bottom of the rad when the car gets to a certain temp the fan will come on and cool the radiator and when cool shut off. Other cars have a fan driven by a belt from the engine in the center of this fan there is a thermostatically controlled clutch which detects the air being drawn thru the rad when the air is to hot the clutch will cause the fan to turn more drawing more cool air thru the rad. When the air coming thru the rad is cool enough the clutch will allow the fan to slip or free wheel. If either type of thermostatically controlled switch goes bad the car will overheat at idle. The car cools down while driving because the cool air is forced thru the rad. Please do not confuse this thermostatic switch with the heater/engines thermostat. I personally would check or take the car to someone qualified to check for a bad electrically controlled thermostatic type of switch on cars with electric cooling fans. On cars that are driven by a belt I would check the fan belt for slippage and the fan clutch it self when engine is cold for oil leakage or when rocked for excessive bearing play and spin the fan by hand to make sure it turns freely then start the engine and allow it to run until the heater is putting out hot air next turn the engine off and spin the fan again the fan should be harder to turn as if there is a drag on it if not I would replace the fan clutch. Electrically operated fans: Parts to check fuses, electric fan motor or thermostatic switch, or an electrical problem. Fan Belt Driven fans: bad broken or slipping belts, thermostatically controlled fan clutch, and cracked or broken fan blades. Check both type systems for a blockage in the radiator core such as bugs dirt leaves. Last but not least if the core if self is clogged internally you might need to flush the system and or have the system pressure checked including the cap. PS Many people on accident put the heater/engine thermostat in backwards this will cause many problems This thermostat is like a one way valve and must be installed in the correct direction.