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MG MGF Technical - Bother in my expansion tank

MGF trophy 160 - year 2002 mileage 47k.
Just had bottom sump oil seal re-done...2 weeks after that headgasket failed - now after 3 days of very careful driving got light steaming coming from expansion tank when car warm...engine not overheating & lots of air / bubble entering return pipe into expansion tank when car is idling. Any body got any ideas or knowledge on this level of bother?
gordon miller

Gordon,

Sounds like the coolant system was not propery bled.

Also sounds like the same may have happened following the sump seal replacement.

If a garage did the work....take it back a moan like hell.

Good luck!

Sam
Sam Murray

Thanks for prompt reply Sam - took it back to garage a few days ago to bleed system again - did radiator, the one under black cowling in bonnet & the one in the engine bay...some air came out but not a lot.
Car back in garage for pressure test of cooling system...but looking at amount of bubbles in expansion tank I am worried that it could be more sinister? soft head or craked liner?
gordon miller

Shouldn't be any need to touch the cooling system for a sump gasket replacement. Was it an oil/water mix type HGF, or did it announce itself in a more dramatic way?

Does your garage use a vacuum fill system? They're by far the best way of filling the F's cooling system.

Cracked liner is a possibility, a leakdown test on each cylinder ought to identify that. I can't see how unbolting the sump & fitting a new gasket could have contributed, the chances of the block being so soft or oddly stressed it's being held in shape by the sump are remote indeed.
Mike Hankin

Strange thing...garage did the pressure test on the collant system & everything OK - then they changed the cap on the expansion tank..to a new MGF one & eveything now works fine in the cooling system - no bubbling expansion tank when hot & idling?
The cap that they replaced turned out not to be a MGF cap...so this has led to all the bother & probabally caused the HGF - which was not dramatic...it just lost all its water & overheated instantly 2 days in a row after 15 miles of driving. It was the garage that diagnosed it as a HGF.
The car is still not right & with garage...is running rough / lumpy & rich? so not sure whats going on?
gordon miller

If it is running rich it may be the coolant temp sensor or connection - the brown one I think.
Tony

This thread was discussed between 05/06/2007 and 06/06/2007

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