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MG MGF Technical - PRESSURE BUILD IN THE WATER TANK

I HAVE A 95 MGF AND I THINK ITS OVER HEATING BUT MY TEMP READ OUT NEEDLE IS SHOWING HALF WAY, RECENTLY I WAS DRIVING AND A LARGE PUFF OF SMOKE CAME OUT OF THE WATER TANK, I WAS TOLD IT WAS THE CAP BUT I HAVE REPLACED THIS AND THE PROBLEM STILL PERSISTS.

THERE IS TOO MUCH PRESSURE BUILDING UP IN MY WATER TANK AND MY OIL TEMPRETURE GOES UP TO 100 WHICH I DONT THINK IS RIGHT.

MY FAN STILL CUTS IN WHEN I AM DRIVING AND WHEN AM ALSO STATIONARY AND AFTER LONG JURNEYS.


CAN ANY ONE HELP
henry

The fan you hear is the engine bay fan which does not cool the engine. It is quite probable that the fuse has blown in the radiator fan (at the front of the car), Check all the fuses if they are ok run the car for twenty mins and the radiator fan should kick in, if it doesn't then there may be a bad connection, undo the connector of the fan, clean and re-connect and that might solve the problem.

Tim

ps no need to SHOUT. :o)
Tim

Sounds like you have HGF, one of the possible HGF's is combustion leaking past the fire rings into the water jacket, this leads to high water pressures (causing the tank to vent) and 'airlocks' causing the engine to run hot (the fan coming on whilst driving).

To check this you can get an MOT man to stick is emmissions sniffer in the tank, if there are traces of HC's in there then its proof +ve.

If you fix it now then you'll get the cheapest type of job, leave it till things go really wrong and you'll need a head skim, copius flushing and an outside chance of a new engine.
Will Munns

Henry, I don't think that the oil temperatures that you are seeing (about 100ºC) are anything to be worried about - especially given the warm temperatures we've recently been having.

Regarding the steam from the expansion tank, it is not unheard of for replacement caps to be faulty - so I'd replace the new one you've got with another before investigating any further.

If that cap blows, then investigate the possibility of a head gasket leak past the fire rings of the head gasket - the suggestion that Will makes i.e. to use an exhaust gas 'sniffer' for hydrocarbons, would be very helpful in confirming the diagnosis.

But cheap solutions first! :o)
Rob Bell

Errm allread done the cap, but it's not unknown for a batch of new caps to be dodgy too, so if you are replaceing it again then go to somewhere else to get it, so dealer if you froght it from halfords, halfords if you brought from dealer.
Will Munns

Exactly what I said Will ;o)

But good idea of making a point of purchasing a replacement from somewhere different to where the last one was purchased. Halfrauds is certainly one option.
Rob Bell

Fine, well I'll take my air of superiority and use it on someone who cares ;-p

(subtext) I ought to read more carefully before implying others ought to read more carefully
Will Munns

ROFL Will - no worries! :o)
Rob Bell

This thread was discussed on 12/07/2005

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