Topic

Hi all,

I put my Mgf which has been off the road for a few years in for an mot recently.

It failed on a few things but the test was stopped as the engine started to get very hot and the cooling fan did not come on. I thought it might be an air lock as I had the engine out just before, but after further bleeding, the water level stabilised and has not moved since. It's not a head gasket as the head and gasket has been done.

My mate told me to disconnect a plug from the rhs of the engine bay and the cooling fan should run and it does.

Is this a temp sender fault? It also failed on CO level being too high. I changed the lambda, so hopefully that is now cured!

Any suggestions are welcome as I don't want to cook the engine!

Many thanks!

At a guess you have unplugged the 2 wire plug from the brown or black coolant temp sensor.

This supplies the ECU with the coolant temp so the ECU can adjust the fuelling to suit the coolant temp.
If the ECU receives no signal from this sensor it will run the cooling fans to protect the engine.
However if the ECU has no signal from the sensor it will run the cold fuelling map thus over fuelling a warm engine.

I would start by replacing the sensor, make sure you get the correct colour version for your car.

The blue single wire sensor is for the dash gauge.

Thanks for your help. Had a dig around today and found the 15a fuse had burst. When replaced, the fans run continuously, so have ordered a new brown temp sensor.
Fingers crossed this does the job!

Changed the temp sensor last weekend and that has stopped the cooling fans continuously running which is great. The engine does seem to take a long time to heat up whilst idling. I ran it for fifteen minutes but the oil temp and water temp gauges never moved. Is that normal with an Mgf? Are they slow to heat up?

It should take about 5 minutes or 3 miles diving to be up to coolant temp, oil takes longer.

Stationary it should take about 20 minutes for the cooling fan to come on.
I wouldn't expect the oil temp to move much.

Ok thanks. I will run it for 20 minutes and check the rad to see if the thermostat is stuck.