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MG MGF Technical - Temperature guage is not working

Hello. I've not been on here for a while as my F has been behaving until recently.
My coolant gauge is not moving when the engine is hot. The oil temp gauge works fine though.
I took it for a drive today and its fine to drive and all the levels were ok. However, when the car idles after a drive the fan doesnt kick in like it normally does. The fuse is fine.
Is this another "common" fault or symptom of something?
I'm of to Australia for 4 months on sunday and don't know whether to ban the wife from driving it.


Here is an extract from a previous post by Spyros Papageorghiou (Nicosia, Cyprus) in 2001, quoting Nick Adams a Lotus Engineer.....

"Hi Per, right, I now have access to the manuals and may be able to shed a little light. There are two temperature sensors fitted to the engine, one which is orientated vertically and which controls the temperature gauge on the dash and one which is orientated horizontally and provides coolant temperature information to the engine management system. The EMS should switch the radiator fan on when the coolant temperature reaches 102 degrees C with the engine running and off when the temperature drops to 96 degrees. When the engine is turned off the fan will switch on automatically at 112 degrees and off again at 106 degrees. The sensors are both resistance based devices which offer a lower resistance as the coolant temperature rises. The normal resistance at 88 degrees C coolant temp should be in the order of 300 to 400 ohms. Any increase in the earthing resistance due to corrosion or excessive sealant will make the sender output reflect a lower coolant temp than is the case. This would give the symptoms you describe. To check if this is the problem run an auxiliary earth line from the body of the horizontal sensor to the negative terminal of the battery. If the fan switches at the right temperature you simply need to remove the sender, clean the threads and reasemble with a little thread sealant. If the fan still switches incorrectly try replacing the sender unit itself.
Good luck, Nick"

Something to try at least.

Its a long way from Aberdeen to Australia.
Hope its a good trip for you. Where abouts in Aus are you travelling?



For those interested further, here's the link to the full topic.


He He, interesting thread, and so many common names down there.

btw, where is Spyros ? Didn't see him since month.

The temperature gauge senders do seem somewhat unreliable - at least the early ones. They're about 9 quid or so...but are a bu99er to reach with a spanner.

I'm not aware that the ECU sender is a problem, if it does fail than the ECU will assume the engine to be at 60 degrees or so and log a fault code.

Oddly enough Nick used to live just over the road from me...he raced a midget for a few years before going over to the dark side with those plastic cars!

alan b

Had exactly that at the end of last year, so I had to sort it before going to the Silverstone track day. Fitting the new sensor was a bit of a pain, but managed it with only a little coolant loss, and lo & behold - temperature normal! Stayed normal at Silverstone, although the oil temperature got quite warm for the time of year....
Mike Cunningham

Mike, why was that? Didn't have the engine under duress did you?

This thread was discussed between 08/04/2008 and 11/04/2008

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