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MG MGF Technical - Overheating

While on a long road trip recently, my 2002 MGF 1.8i started to overheat whilst stationary in traffic.

Turning the heater on to max always brought it back to normal.

I did not wait to see how hot it would get before doing this!

The fan comes on OK.

It's only done 16,000 and very rarely goes on very long journies.

Any ideas chaps???
Sam Murray

Sam

Two things spring to mind:-

1/- Air lock in coolant system.

2/- Are you sure the Radiator fan comes on - the fan you normally hear is the engine bay fan.

Plenty of advice in the archives on how to check and cure both of these problems.
Ted Newman

Sam, is your coolant still showing as full? If there are dribble stains around the cap, the valve may have failed so try a new cap. I think even in 2002 the caps being fitted were what a limited MGR budget allowed, and not far off being called a consumable item.
bandit

Thanks guys.

No sign of any coolant loss at all.

Good point about the engine fan...I hadn't thought about that.

Pissing rain today, so it will have to wait.
Sam Murray

The other thing to have a look at Sam is your radiator. Irrespective of mileage, they fall to bits after a few years and yours might be showing it's age.
David Clelland

Another good point David.

Still pising rain though :-(
Sam Murray

Sam - this is almost certainly non-operation of the radiator fan. The commonest cause in my experience is failure of the engine management's water temperature sensor (simple and cheap replacement - http://mgf.ultimatemg.com/group2/common_problems/hgf_pages/related_problems_overheating.htm)

The other is a failed fuse (also mentioned in the above mentioned link). Very rarely the fan can fail completely, or the rad sludge up - but the latter would be expected to show up in road usage when driving at speed...
Rob Bell

Hi guys,

The radiator fan had blown. I replaced it and let the car idle until hot. The fuse blew again.

I suspect a seized fan.

Any advice on fixing or replacing it, before I start taking the nose off the car???

Cheers!

Sam
Sam Murray

Have you changed the rating of the fuse? I wouldn't normally advocate this, but as Dieter found out, MG Rover did exactly this themselves to prevent this problem on later TFs.

And yes, I would expect that your problem lies with a slightly sticky fan (bearing needs a little lubricating perhaps? Not looked into this myself yet, so not sure how to retrieve a 'sticky' fan...)
Rob Bell

Rob,

Sam's car is slightly newer than mine and I have the uprated fuse as standard so I'd expect Sams's to be the same.
David Clelland

20A DC?
Rob Bell

"20A DC?"

Yes
David Clelland

Sam,
Before you disassemble too much; can you try and rotate the blades from underneath with a long screwdriver or similar. If a piece of debris has ended up even slightly jamming it, the instantaneous startup current would be suitably enormous to blow the fuse without major damage to the fan motor. A well wedged insubstantial twig or a plastic bag would be plenty strong enough to do it. HTH
Charles

Crawled under the car yesterday.

The fan turns very easily.

I'll "upgrade" the fuse and see what happens!

Sam Murray

Cracked it boys!

20 amp fuse does did the trick.

I suspect the fuse blew the very first time the sensor asked the fan to fire up.

BBS comes the rescue yet again.

:-)
Sam Murray

Nice one :o)
Rob Bell

>I suspect the fuse blew the very first time the sensor asked the fan to fire up.

Well spotted.
I assume half of the HGF from between 1996 and 2000 related to that Fan Fuse problem.

The higher fuse spec. appeared in 2000
http://www.mgfcar.de/fuse/index.htm

Regards
Dieter
Dieter

Hi Guys

I read lots of the articels in the Archive and this post here and still have issues with my fans not kicking in:

- Both fans tested indivually when I replaced the radiator, the work, not stuck.
- When I remove the connector from the temp sensor, both fans (I have Aircon) go on, so the circuit must be working.
- I have the stronger fuse in place.
-I have replaced the sensor with no result.

Today I noticed my slam pannel just above the radiator gets so hot when the car is standing that water on it evaporates and yo burn your fingers touching it. Guess at this temp the fans should go on.

Oil temp is arround 90-100°C

Any other Ideas?

Rgds,
Cyril
Cyril

Water pump?

Chris
Chris

Chris, I don't think the waterpunmp is an issue, I get the coolant flow, it's just that the fans don^t start to operate.

Any other ideas?
C. A. Winkler

This thread was discussed between 20/06/2008 and 02/07/2008

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