Topic

The engine bay cooling fan comes on immediately the car is started. After stopping the engine the fan runs on for a few minutes (even when engine cold) and then stops.
So I'm suspecting a thermostat/sensor somewhere is at fault, but have no idea where it might be located, so hoping someone will be able to point me in the right direction.
Thanks in anticipation

Depending on age of car, sensor is located just behind the coolant header tank, on the bulkhead between boot and engine compartment.

It is screwed into a small bracket.

On the newer chinese cars, I believe it was omitted, and uses other inputs from ECU to run it.

The TF also disposed of the separate sensor and uses the ecu to trigger the engine bay fan.

If you have a MGF or early MG TF it will be engine bay sensor mounted on bracket above coolant expansion bottle.

If you have later MG TF, inc SAIC then it will be a faulty water temp sensor back top left engine behind air filter. There are two. One feeds the Water Temp Gauge, and the other feeds the ECU. Its the ECU one you are after. Could be Brown or Black dependant on age of car. Blue one next to it is for Temp Gauge.

When sensor is open circuit / unplugged cooing fans come on with ignition, the engine bay one should cut out on timer (8 min?) after ignition off if I remember correctly.

Cheers, Mark

Thanks, all. Turns out my TF (03 reg) is old enough to have the sensor mounted behind the coolant tank. It was just a case of dirty contacts - so a nice easy (and cost-free!) fix.

Result !

I've got a late '04 TF, so no engine bay sensor and I've had a similar issue, however with the engine bay fan running if I turn the ignition off the engine bay fan goes off - no run on as suggested here? Is this correct?

I've got a late '04 TF, so no engine bay sensor and I've had a similar issue, however with the engine bay fan running if I turn the ignition off the engine bay fan goes off - no run on as suggested here? Is this correct?

No, the engine bay fan should only come when the engine is really hot in summer. I only noticed mine running once last year. If the engine bay fan is running because the engine is hot it will continue to run after ignition is switched off until sensor has detected temperature drop. (Different temp dependant on model and engine type.), or times out.

If engine bay fan is running with ignition on and stops when ignition is switched off then sensor has failed safe (open circuit) or has become unplugged.

Cheers, Mark