In today’s modern vehicles it is considered normal for the engine cooling fan to keep running for a few minutes even after you turn off the car. The cooling fan or fans are mounted right behind the radiator which is at the front of the vehicle behind the front grill. Here is a picture of the cooling fans that stay on, when you turn off the car.
In fact, in some vehicles, the fan may run up to five minutes and sometimes longer. The reason for the cooling fan to continue running is help the engine to cool. When the engine is running; the coolant circulates from the engine and flows to the radiator where heat is dissipated. Moreover, when the engine is turned off, the coolant stay stagnant in one spot, and the heat stays trapped therefore prolonging the engine from cooling. With the help of the fan running when the engine is off; this will help speed up the cooling process.
In most vehicles, the coolant temperature fan switch sends a signal to the PCM to turn on the fan when the hot temperature is reached. For example, the fan can turn on when it reaches 110 degrees Fahrenheit. Also, in warm weather; the fan will turn on more often than compared to colder weather when the engine is off. In a way, this protects the engine from unnecessary overheating which can lead to premature head gasket failure.
Cooling fan stays running common causes
Here are some other possibilities the fan may stay running longer.
Possible causes the cooling fan may stay running are:
low coolant level,
faulty coolant temperature sensor,
PCM or ECU defective
coolant leaks from the water pump,
worn upper or lower radiator hoses,
leaky heater core,
leaky thermostat housing,
rusted coolant bypass pipe,
bad radiator fan relay,
short in the electrical wires and so on.
If the fan continues to run for more than 30 minutes; disconnect the negative side of the battery cable to prevent the battery from being drained.
To test for a bad fan relay; simply swap the bad fan relay with a good relay with the same pin design. Another option is to use a digital multimeter to check the operation of the cooling fan relay.
If the fan turns off, that means the relay is at fault.
Furthermore, check for low coolant level and possible leaks that may be causing it. Usually, low coolant will equate to a hotter engine, therefore, it will activate the fan more often.