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MG MGF Technical - Another Head Gasket question...

I've replaced many head gaskets on Fs and TFs very few have given problems afterwards.

However, I've had two with issues, both the same problem...

Fit the Multi Layer gasket as recommended by all. I get a coolant weapage from the head joint under the exhaust manifold.

The first I rectified by going back to the old single layer gasket with the silicone bead, this has sorted the problem.

The second I am tempted to use the Composite type gasket (GUG702577HG).

Has anyone any comments on this type..?

Thanks in anticipation,

Mark.
M T Boldry

Hopefully someone can shed some light on this - but unfortunately, I have no direct experience...
Rob Bell

Could it be the liner height above the block?

Anything up to 3 thou would seem to suit a polymer bead gasket, anything above 3+ thou is multilayer shim country.
Don't forget the block expands more than the liners, so little liner standproud is accomodated by a polymer bead gasket.

I replaced by beaded gasket two years ago on 3+ thou with a multishim gasket, no lower oil rail, and so far so good.

I think the LE500 cylinder head had enlarged coolant passages, perhaps to overcome any local hot spots which may well affect the bonding of the bead, which after a lifetime of battering, gives up anytime!
Just my theory.

I don't think there is a standard answer, it all depends what you find when the head comes off.
Jerry Herbert

I agree with Jerry.

When researching information for my engine rebuild I discovered that the MLS gasket type works best when all the liners protrude by the same amount (3+ thou) with no more than 1 thou difference between them. Of course the head must not be warped nor porous, either of which might be Mark's source of a weeping head problem.

Jerry's point about waterways is interesting. Part of the refurb work I did was to fettle the water passages in the head with a Dremel - some were partially blocked with casting snot.

Jeff

J Lennon

Jeff and Jonny, As mentioned above, this car is a constant source of problems. It's TF VVC with only 23000 Kms on it from NEW...! The car is pampered by it's owner, warmed up before use, never revved hard or in any way abused. I'm sure that Land Rover Freelander owners have commented on similar problems but as yet, I've not seen any cure for the weaping from under the exhaust manifold.

So, does anyone have any comments on the Composite type head gasket...?

Cheers,
Mark.
M T Boldry

Mark

I supplied a composite gasket once. It was a disaster and failed almost immediately. A costly lesson by the time I met the warranty, never again.

Multilayer gasket: the coating dissolves in glycol apparently, so weeping is not uncommon - usually very minor. There are two approached to addressing this:

1. The coating cures by heat. Run the engine before introducing coolant so the block/head interface gets to about 65 degrees C IIRC. That's about a minute I understand. A bit hit and miss if you ask me but I know it is a method used successfully.

2. Use a different coolant - the organic acid type, aka OAT. Techinically referred to as a corrsion inhibitor rather than anti-freeze. Draw-back - reacts with glycol so the entire ccoling system must be well flushed first.

Me? I'm happy with the original gasket, 300 000+ miles between two cars and all is well.

Paul
Paul Walbran

"dissolves in" might be a bit strong. Certainaly reacts with glycol
Paul Walbran

From Jerry, aka "Jonny", I think you have missed the point I was making, as well as possibly my name!!

The multishim gasket has one "sticky" surface, and that is facing up onto the cylinder head. If the liner height is not within spec, the spring s/s shim gasket won't be able to seal properly. The exhaust side is probably the worst as it has to cater for the torque reaction of the exhaust manifold and subsequent flex.
As for "dissolving" the coating, I find that impossible to believe. They wouldn't make a gasket which did that, and I've never seen one that has done that. More likely to be fretting between the gasket and the cylinder head near the exhaust manifold due to insufficient clamping loads.

The multishim gasket is not a cure-all, you need to establish the dimensions aound the liner/ cylinder block, condition of the head etc before deciding which type of gasket to go for.

Just to correct another misconception, OAT is glycol based, it just has different corrosion inhibitors. It will mix with "old fashioned", but can sometimes give rise to some sludgy products. OAT is the default coolant for most manufactures worlwide now, and gasket makers would never make gaskets that are incompatible with OAT, or older glycol mixes.

When you say the problem keeps re-occuring, it strikes me you haven't got to the root cause of the problem, which is most probably the dimension checks mentioned above.

I could be talking out of the back of my head, I'm not sure about a third "composite" type of gasket though.

Jerry
Jerry Herbert

Jerry

We just supply these to the trade, don't fit them ourselves. The feedback I cite is from people in the trade very experienced with these engines and well aware of the critical dimensions you mention.
They take either of the steps I outlined above and have never had a problem since.
Paul Walbran

Jerry, sorry for the Typo...!

We've got 0.0015" liner protrusion equaly on all 4 liners. Once we took the head off again today we found evidence of water leaks on both inlet and exhaust sides of the head gasket.
It's clear that the gasket has sealed on the face of the head and also the face of the block. The fire rings are all excellent and show that they have sealed perfectly on all cylinders.
The leaks appear to be coming from between the layers of the multi-layer gasket.

"When you say the problem keeps re-occuring, it strikes me you haven't got to the root cause of the problem, which is most probably the dimension checks mentioned above"

That's the problem... I don't think we have got to the root of the problem, I wish we had....!

After talking to Paul on the phone today, I've decided to use the shim gasket with the silicone beading. (I carry all three types in stock...).

I'll let you know....

Mark.
M T Boldry

The elastomeric gasket is the preferred one for me, the MLS gasket is poor when liner heights are low, high or uneven and when the block surface is not perfectly flat.

The Elastomeric type is far more forgiving. The only time an MLS gasket has an advantage is when there is porosity on the surface of the head or when compression ratio is too high due to excessive skimming and needs to be lowered. This is based on over 500 head gasket replacements.

To make a lasting repair.

i) ensure the liner heights are 3-4 thou
ii) ensure the head is harder than 95 brinell
iii) ensure that the head is flat
iv) if possible peen the fire ring area of the ehad and have it skimmed, this will eradicate porosity on the fire ring which is a major cause of repeat HGF
v) use a Payen BW750 elastomer gasket
vi) use new OE head bolts.

Dave
Dave Andrews

Thanks for the info Dave :o)
Rob Bell

This thread was discussed between 07/09/2011 and 19/09/2011

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