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MG MGF Technical - Help

Hi Guys,
looking for some help, (99 VVC) car appears to misfire at low revs but appears to pull great at higher revs, no smoke, no rattles , no overpressure in the crank case, a little water at the exhaust shiney bits after start up when cold.

Carried out compression test

1 and 4 good

2 and 3 (almost zero)

No water in the oil
No oil in the water

Is it Head Gasket or valves

or both

or some other horrible ailment

How difficult to remove the head in situ
or is it better to remove engine

Clive
Clive Skelhorn

Clive, the fact that it's 2 & 3 I agree suggests the gasket has failed between them, that seems more likely than valve failure (unless there has been prior stress, e.g. cambelt failure?) and the fact that the engine seems to run well at higher revs suggests that only the head needs to be removed. This is usually done in-situ, back-breaking but less work than loosening the entire rear subframe. If you replace the gasket with the Land Rover version, the modified oil ladder it requires can be fitted with engine in-situ still, so again head removal is sufficient.

With just the cam cover off you should be able to detect a stuck valve with feeler gauges, that may give more indication of best approach.

When the head is off you'll be able to check the piston liner heights - if a gasket has failed between the two fire rings, it may be as a result of a liner having moved. Agreed, you may at this point discover that you're ditching that engine and have to unbolt it, but that's last resort...

Happy spannering ;o)
bandit

I thought the liners were held down by the head? If you pull the head and roll in gear the liners move easy. One useless garage once wanted to pin the liners, make sleeves etc, only an expert on K series told me they would move with the head off. Full rebuild, many miles later, I'm inclined to beleive him. HOWEVER, you may have had movement of the head (overheating and bolt stretch) and HGF, this may lead to liner movement. Go to a good garage.
RD MADGWICK

Thanks for the help guys

Clive
Clive Skelhorn

This thread was discussed between 06/08/2008 and 11/08/2008

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