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MG MGF Technical - DIY HGF Repair Advice Needed

I have a 1998 1.8 mpi 91,000 miles and still on it's original gasket (if the service records are correct) but just bought a 1998 MGF Abingdon1.8 VVC with a blown head gasket as a second car to tinker with. Too good a deal to turn down - Full Walnut leather, chrome accesories, abingdon 16in alloys (plus new headlights according to their 2005 date stamp) AND pristine hardtop, all for £500...

It's a definite HGF - Gooey yellow oil all the way up the dipstick and present under the main oil filler on the top of the engine. I've bought my cam locking tool, flywheel locking tool and I have worked out how I'll clamp the liners once the head is off... But, before I get that far, I thought I'd try a quick compression test: 3 cylinders pretty much the same and cylinder 3 about half that of the others.

Now to my question. I've topped up the water and checked for obvious leaks on the pipework - None! (although the intricate collection of rubber pipes at the back of the engine is brand new, so I assume that this was the likely cause of the failure). Anyway, I topped up the reservoir and it took about 2 days for the water to drop significantly (and the Mayo to climb further up the dipstick tube, or is that just my imagination?). Is it posible that the water could be draining into the sump? Or would that signify a significant breech in the gasket (and perhaps indicate a warped head), or is this something that can happen?

I'll know soon enough when I get the head off but I thought I'd just ask the question...

If all else fails, I could break the car and get my money back (just a shame to see the end of a limited edition).
Mark Clayton

the gasket keeps five things apart

High pressure oil to the head
Drain down oil to the sump
Water
Combustion
Outside

A failure between 2 and 3 is quite common. or a total breakdown caused by a breach between 3 and 5 which is not caught before major overheating occurs.

You don't need to clamp the liners unless you're moving the pistons (which you should not need to).

If you take the head off and find it has been freshly changed then it might be a cracked liner :(


Will Munns


http://www.carlibrary.ru/lotus/elise/service/01_lotus_elise_s2.pdf

has the engine manual embedded, print it off before you start
Will Munns

Cheers Will, I wasn't sure about clamping the liners - I don't intend to move the pistons but I read that you should clamp if the head is off for any length of time? I haven't bought the gaskets etc yet in case there is more damage than I'm prepared to take on, so I thought it might be wise to plan how I'd clamp them just in case (read your block of wood suggestion). Do you think you could leave it unclamped, or do the liners 'relax' over time and compromise their bottom seal if pressure is not applied?

I know the person I bought the car off and have all the service history (lots of MG service history), so no recent failure for sure. No sign of an old HGF in the documents; some old references to water level dropping, replacement of underfloor pipes & rad - another referring to replacement of water pump - but they are all a few years ago. Hoping it's just the simple 2 & 3 as you say...

Thanks for the help
Mark Clayton

This thread was discussed between 29/04/2009 and 30/04/2009

MG MGF Technical index

This thread is from the archive. The Live MG MGF Technical BBS is active now.