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MG MGF Technical - Coolant collecting on spark plugs, where from?

Back again with the same unresolved problem, now worsened.

I have coolant collecting on the tops of my spark plugs around the plug leads of plugs 2 and 3. This has been building since May, but since I wasnt seeing appreciable coolant loss I could put it down to condensation, not leaking coolant. Now however, I am suffering coolant loss and the (quite deep) puddle around the plugs is greenish and smells of ethylene glycol. Compression is comparable between all cylinders hot and cold. With the engine hot, condensation forms rapidly around a cold plug wrench inserted down 'plug holes' 2 and 3 , but not 1 or 4 so it does seem to be escaping from the head.

So what is it, other than expensive? Are there any joins/gaskets in the head above the spark plugs which could be leaking, or is it a cracked head? It cannot be the HG because thats below the plugs, although I (probably erroneously) had that replaced 3 weeks ago because oil was starting to contaminate the coolant. The elastomer rings around the oil channels on the old head gasket was showing signs of breakdown. However, I cant be sure that the oil/coolant was mixing because of the gasket or because of this (cracked head?) problem. There are still traces of oil in the coolant, but that could easily be residual.

Car drives perfectly, until the water interrupts the spark which is evident as a misfire.

Has anybody experienced this? What can I do? Advice will be very much appreciated!

P Davey

Not sure you should be driving it in that condition, so you should ring up the garage to see what they suggest.

If you asked them to fix the problem without being too specific, you are in a strong position to bargain, but if you just asked them to replace the HG and that was not the problem, you might have to put it down to experience and pay up again.



Well, I'm not driving it but that's because I'm afraid of it becoming undriveable, I can't see it getting much more expensive than it already is!

Anyway, I asked the mechanic for a gasket change, and since I've no evidence of gasket failure I shant be chasing them. I just want to know what is wrong.

Annoying thing is there's been no overheating to trigger this (and my low coolant alarm only triggered once, pulling onto my drive on saturday, never before this problem) so it looks like a manufacturing defect.

Can anyone confirm that this is a cracked head?

P Davey

It can't be the head gasket as that can only leak onto the other side of the spark plug - ie into the combustion chamber. The cam carrier doesn't have any coolant feed running through it's mating face with the head so there's no way it can come from there.
I don't recall the waterways near the head surface going close to the spark plug recesses to be able to leak through.

I can't help but suspect that the coolant gathering there is a secondary effect - a split pipe might be spurting coolant onto the top of the engine and it's pooling in the spark plug holes. If you can pressurise the system, or run the engine up to temperature, with the engine bay cover off and watch for leaks then you might find a jet of coolant from somewhere. I know it may sound unlikely but I had a tiny hairline split in a hose which was invisible in situ but sprayed everywhere when te engine warmed up.

Alan B

I presume the spark plug cover is in place when the coolant appears? That would make the coolant coming from outside the engine less likely, and point towards a crack in the head. Have you tried packing the plug recesses with kitchen roll? That might give an indication of which direction the coolant is coming from.

Perhaps worth confirming with the mechanic that re-fitted the head whether new stretch bolts were used, and how they were torqued. But as the symptoms pre-date that procedure it does look like a crack - very unlucky 8-(

The coolant collected with the plug cover in place, and I ran the engine up to temperature with everything off when we compression tested it, no sprays of water anywhere, just significant vapour condensing on the plug wrench down the middle 2 plug holes. So presumably I am looking at a new/replacement head (I'm assuming its not worth repairing a head). That's 300 odd on ebay 2nd hand, around 700 reconditioned (and a similar price for a whole Rover 200vi/early MGF with MOT!) and prohibitively expensive if fitted by a garage to a 9 year old VVC. I am tempted to have a go at replacing the head myself next spring (when funds and daylight hours are available - how hard can it be?)

In the meantime I'm afraid I have bought some snake oil [K-seal]. I expect someone will tell me that it will destroy my engine/radiator/soul etc, but I haven't found any 1st hand experience of any directly attributable damage caused by k-seal and my head is already a write off. I am moving house on friday and need the car to get me to our new home (this also explains the lack of funds). After this I intend to drive the F cautiously to see what impact the k-seal has had, if any. Interesting stuff this K-seal, its a bit like putting copper slip in the coolant. Quite festive actually, having all these sparkly bits in the coolant. Anyway I digress, will report back on results at a later date.

P Davey


I have a freshly built (6000 miles) 1293 A-Series in my midget - putting out in excess of 75 BHP.
Apparently an MGF A-Series conversion is ultimate dark-side stuff - as you're local I'll happily do you a straight swap - even with the damaged head.

Call it pre-Festive generosity.

Steve Clark

This thread was discussed between 23/11/2008 and 02/12/2008

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