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MG MGF Technical - Overheating

I have just bought an MGF Convertible around 8 weeks ago, it is a W reg with 29,000 miles on the clock. Have had it at the garage (Arnold Clark) twice as the car seems to be overheating. Temperature gage starts to move up and then all you can see is smoke coming from the boot. The first time Arnold Clark said it was a water pump, which they replaced. Got the car back yesterday and they said they changed a fuse and put in a new cooling fan. Travelling to working this morning and the temperature gage began to rise again. Does anyone have any ideas?
Jackie

err which Arnold Clark in Glasgow?

not the one near the SECC by any chance?

paul weatherill

It was Arnold Clark at Mount Vernon.
Jackie G

1) Sensor; there are two, one for the gauge - which appears to be working!, and the 2nd feeds the control computer which should switch on the front fan. Do you ever hear the front fans ?
Hopefully the garage would have tested this - but it appears not?

2) an air-lock. common in an MGF - you just need someone who knows how to bleed the coolant system.

An MGF should be able to cope with any traffic, in any UK weather conditions without ANY overheat problems.

To test, just let it idle till the front fan comes on and make sure it turns off again. the gauge should rise to about half-way and then not budge. The garage should have done this before you collected the car.
Steve

Jackie - does the temperature tend to rise when in traffic, and fall again once you get some speed up?

It could be something very simple: a problem with the engine management's water temperature sensor. It is fair common for these to fail, but their replacment is cheap and easy (around 10 quid).

Other things to check is the operation of the front radiator fan - has it jammed, is the fuse okay, are the connections good?

But I'd replace the sensor first, and see how you go.

See http://www.mgf.ultimatemg.com/hgf_pages/related_problems_overheating.htm for more information :o)
Rob Bell

I only hear the fan coming on when I stop the car completely. It this norm, as it is my first MG I don't know too much about it! The garage told me they let the car run for around 30 minutes yesterday with no problem.
Jackie G

But start with the really cheap and easy...

Go to halfords and get yourself a new coolant cap (less than £10), it might just be that the system can't pressureize - this is a very common fault.
Will Munns

>I only hear the fan coming on when I stop the car completely
There are two fans, one in the engine bay (vent on side of car) and one under the bonnet, it is the under bonnet one we are concerned about (jump out when it next overheats and listen, it's quite obvious from outside the car)


>The garage told me they let the car run for around 30
>minutes yesterday with no problem.
could be a partially sticking thermostat, but if so I would expect the temp to rise when on a dash, but not when sitting in traffic (unless you had just been on a dash)

Will Munns

Rob - the temperature does tend to rise in traffic and if waiting at lights etc, in fact last week I was sitting outside a shop for around 5 mins with the engine still running and the smoke that was coming out was incredible, in fact when I opened the boot the water was at boiling point!!
Jackie G

Also, replace the Cap on the Expansion tank. If the car has over heated this will be U/S and will certainly happen again. A replacement cap is only £3.50.

The pressure cap works by increasing the pressure in the coolant system. Higher pressure means a higher boiling point and better cooling capacity. If the cap has failed then the boiling point will be too low. Also if the cap has failed the increase in the temperature of the coolant will make it expand and the easier place to come out is through the expansion tank.
tim woolcott

Sounds like a coolant cap to me.

SF
Scarlet Fever

>in fact last week I was sitting outside a shop for
>around 5 mins with the engine still running and the
>smoke that

Eeek, don't do that, if you let the car get hot then you have a sure HGF on the way, if not a whole new engine!

Will
Will Munns

PS don't replace the cap when the car is hot, you run the risk of SERIOUS injury........Wait for the car to cool right down.

When topping up the coolant never fill above the seam of the expansion tank. When hot the coolant should never get much above this mark either. Recently I noticed the coolant in my car had almost reached the neck of the coolant tank. I immediately replaced the cap and now no more touble.
tim woolcott

Thanks everyone for your comments, it's much appreciated. Will let you know how i get on.
Jackie G

Yup, replace the coolant cap - although this only responsible for the coolant boiling off. It doesn't cause overheating per se (unless all the coolant has gone!).

The fact that the temperature rises in traffic points to the temperature sensor, which in reality is only a couple of quid more than the coolant cap.

Worth replacing yourself (or call a friend!)
Rob Bell

jackie

please check your email ....gerry
gerry

Gerry - checked my email, there is nothing there.
Jackie G

jackie

ihave tried again ...sorry ....gerry
gerry

jackie

can you chk your email above as i can only get a failure notice when i send.gerry
gerry

Gerry

Try jackiegentlesuk@yahoo.co.uk
Jackie G

Sorry to say but the MGF is gonna have a Blown headgasket. These cars are having more trouble than their worth & over here the parts prices are ridiculous. They become an ongoing repair once they boil. From factory they come out with design faults. Neverends. Sorry to give bad news, but i've worked on too many of them. Alloy, cast & heat dont mix.
Peter

This thread was discussed between 18/06/2003 and 20/06/2003

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