On my 1.3 MPI felicia there is something which looks like some kind of sensor screwed into the radiator (with wires attached). If you look into the engine bay from the front of the car its on the bottom left of the radiator.

What is it? Because the temperature sensor is next to the thermostat??!!

Also, any ideas to stop the joint from leaking?

Cheers guys

That's the fan switch. When the radiator gets above a certain temperature, usually when the car is sat idle and not getting enough air flow across the radiator to cool it, it turns the fan on and turns it off once it has reached a certain temperature.

As for stopping it from leaking it's probably best to buy a seal. The seal is either part number N 013 827 2 or for vehicles from 10/97 onwards 6U0 959 895. These should cost next to nothing from your local dealers.

To replace the seal, it may also be ideal to drain and fush the cooling system and add new coolant if this has not been done for a number of years. Otherwise remove the wire connectors and unscrew and quickly block it off with a cloth. Clean the sensor, remove old seal, put on new seal and remove cloth quickly then screw in. Replace wires.

After this, to make sure there is no air in the cooling system run the engine with the coolant cap off (drape a cloth over the opening to prevent coolant spashing on paintwork) with heater contol on full and wait till the fan cuts in and turns off. Then stop the engine. Let everything cool down and top up coolant to proper level.

Lovely, yet another fantastic answer.

Thankyou

Out of interest, could the joint be sealed using PTFE tape? Its generally pretty heat proof as its ok on hot water internal plumbing.. or would it react with the coolant?

Just a thought as the seal currently on it is still rubbery and seems quite ok. Will order one next time im going past my local dealership though.

I think there's been some mention of someone using ptfe on a car coolant system on these forums and it working, and afterall it is a threaded joint, so could be worth a try.

It'll normally only leak if the fibre washer has disintegrated. In that case, I'd just try to scab a new washer off your local motor factor. PTFE tape won't react with anything (I mean ANYTHING) but won't necessarily fix the problem because it's intended for use in taper-thread plumbing and the fan switch has a parallel thread. I'd rather go for no washer and just lots of red Hermetite all around.

Thanks for the reply Richard

Its going to be a few weeks before ive got time to attempt anything, the leak is small so its not majorly important. I think ill do a full system drain as I'm replacing the thermostat at the same time.

Will update this thread when I've sorted it.

Cheers