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MG MGF Technical - Advice needed

On the way in this morning, looked down to see temp guage in the red. Pulled over looked for coolant leaks, mayo in the oil etc with no sign of anything amiss. Started engine again, temp showing normal. Hot air coming from the vents. Continued in the last 6 miles at a slow rate, just in case. Watching the guage more than the road, it would suddenly shoot from normal to red in an instant, sometimes staying there other times dropping back to normal.

Just been out in her again and the same thing is happening. Loose connection? dodgy stat? dodgy temp sender? warning of HGF? all opinions welcome.
Richard P

Q's

Is the coolant at the right level in the tank?

When hitting red is the heater in the car working, is it overhot or overcold?

Does the fan come on when above norm?
Will Munns

Coolant level is normal.
Air vent temp stable.
Not sure about the fan but was travelling at 60 at a steady pace on a cool morning so I don't think it was overheating cause of that.
Also the way it jumps from norm to hot on the guage, I would have thought it was too quick for a real temperature change to have happened.
Richard P

You should be careful, the gauge might jump because it has no water (conduction only), followed by a rush of steam. My question about the fan is to find out if the ECU thinks it is overheating, cause if it does then it probebly is!

The heater takes a little time to react, but steady temp air is a good sign generally. If the temp connector wire has rubbed thru against some metal part then this would give you you rapid jumping effect.

The only other thing might be a thermostat problem causing the car to run hot, with occasional boiling causing steam bubbles going past the sensor, but the wire sounds more like the culprit.
Will Munns

Can you point me to the temp sensor,
cheers
Richard P

:)

just been out to check again, cars been off for 90mins and the temp guage is still in the red. :)

Richard P

Phew!

Sounds like it's the guage then and not an indicator of 'something that shall remain nameless' ;-)

SF
Scarlet Fever

Take engine cover off, in centre of bay you should see a pipe exiting the engine, it has two sensors on it, one is brown and has two wires, the other is either black or blue and has one wire, switch on and wiggle wires around, if gauge jumps about then the fault lies nearby!
Will Munns

Cheers,
I'll get the cover off tomorrow and have a look. I'll let you know the outcome.
Rich. (now smiling and feeling much happier)
Richard P

The gauge reds hot when the resistance across the sensor is low. If this is occuring erroneously here, then I wonder if there may be a short somewhere along the line?

In any case, Will's suggestion is what I'd be doing too - the harness near the sensor itself (the blue one mounted vertically under the engine coolant outlet stub manifold on the left front corner of the engine) is where it is most vulnerable to breaks etc...
Rob Bell

itis one of the temp sensor's ,just had mine done £35.00.
William J.Reid

Cheers Rob.

Just driven home (a fool you may say.) But two seconds after starting it it started bouncing from cold to hot and as the engine warmed up, bounced from normal to hot. 99.9% sure it's the cable or sensor.

Will keep you posted.
Richard P

Thinking about it Richard (and William's comments confirmed it to an exent), I'd be suspicious that it is the sensor itself that is at fault. They usuall cost somewhere in the region of 15 quid from Rover - and are a doddle to replace DIY (I've had to do the ECU temperature sensor more than once - annoying more than anything)
Rob Bell

Rob,
Just in case it is I asked the garage who normally does car work to order me one for the morning. Sale or return.
ps I'm doing the work myself, it's just easier for them to get the part than me.
Richard P

Wow, you've got an understanding parts department there Richard - usually MG Rover have a policy of not accepting back special order and electrical parts.

Fingers crossed - but I reckon this'll solve the problem for you :o)
Rob Bell

Appears to have been the sensor. Now changed. The drive home will let me know for sure.
Thanks all for your help.
:)
Richard P

This thread was discussed between 19/04/2004 and 20/04/2004

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