Citroen XM Forum

When I pulled the head off the SED, the gasket was a steel laminate type, it does seem to have de-laminated as the head was lifted. I didn't strip the engine because of a specific problem, I just thought it would do 'us' good to get to know each other and replace a few bits and pieces along the way. Anyhow when I went to the local engine re manufacturers I asked him about the head gasket situation and he showed me a book with the different options in it - 1 notch, 2 notch, etc, laminate, etc. The book also gave thickness details, the difference between the thinness and the thickest was tiny (about 1.some mm I think). I chose to go for a laminated FAI one that cost £40 +VAT.

The chap commented that the head needed 'skimming' because although it could be within spec the surface of the head wasn't smooth enough to ensure a lasting repair. This could have been bunk but it makes sense to me and considering the amount of work involved it was worth having it 'skimmed'. All in, pressure test, clean, 'skim', headset and gasket it came to just shy of £150 Inc.

Steve.

Hi Steve

I had mine skimmed as well, it wasn't far out but in view of the work required to change the gasket I didn't want to take any chances, I even fitted a new radiator , it subsequenly served me well, 70k without missing a beat. I didn't have it pressure tested as it hadn't boiled and I had no reason to doubt its integrity, in fact I have never heard of one of these heads cracking, unlike the 1.9! The cooling was vastly improved on the 2.1 with the whole system being redesigned.

Peter

Dieselman wrote:Paul.
Was the new laminated gasket noticably different in thickness to the regular sintered one? I've spoken to a reconditioners today and they said unless skimming the head just use a regular gasket.

I'm confused now, but might use a regular one as the original one has been on nearly 20 years anyway.

It measured around the same!

Will IF THE CAR has NOT BOILED Put a Laminated one on with the same notches!!!

Seriously! You wont want to be dooing it again 1000 miles time or less! Mine had been done with an ordinary, and had blown as it had!

Dont waste your time! Laminate her!

Paul

Hi all,i'm with Paul.Citroen only supply ONE thickness of laminated HG for the XUD11,and it's called a "repair gasket" for a reason.After cleaning the head/block faces check for flatness,particularly if it's boiled,only then need you consider a skim.The "repair gasket" will take up a lot of irregularities.That's it job,or you would just measure up and select one from the various thicknesses available.The head bolts are one shot only,so don't scrimp here.I've done 2,with "repair gasket" and new bolts,they were permanent repairs.
robertm

What bothers me is the 'repair gasket' being thicker because it is designed to be used after a skim. This alters the compression ratio slightly so could lead to harder starting and less efficiency.

At the moment I've no reason to believe I will need a skim as the gasket is only just leaking compression gasses into the water, which I'm sure is just a result of the age of it.

Hi Dman,in neither of my cases were there any noticeable starting,running or performance issues,far from it.My own SED was ROTODIESEL and my daughters SD a BOSCH.The difference range in the 5 gasket thickness's is only 0.2mm.Note also, bolt thread and head are lubed.I suppose if you're really curious you could do a compression check after the repair.
robertm

Gasket thickness doesn't make as much difference as you think, it always knocks the performance and starting when you take the head off and disturb the coke, but within a few thousand miles it will heal up.

I used to use quite a number of Perkins 4/108 engines, they didn't do different thickness gaskets, you had to machine the top of the pistons to give a specified projection. One engine I had reconned they hadn't done the machining so the pistons were full height, they didn't hit the head but it was the only one of those engines I ever had that would start without the cold start aid, which virtually blew a flame down the inlet manifold - and those engines could be a pig to start.

Peter

I actually got the Laminated gasket to the SAME SIZE as the original that was fitted .. 3 notches!

Id tend to disagree with you peter about gaskett thickness!

I fitted a gasket - after a head skim to a Xantia HDi engine.. the gasket was the thickest available.. after fitting and all reassembly the Compression had dropped completely! almost to zero compression... the car would run though.. the owner decided then for me to pull the engine out and put another one in!

So - I personally - think the Thickness on these XUD's is fairly important to keep the compression ratio correct...

Paul

Hi Paul

I'm not saying that it doesn't make any difference but the engine will normally run and drive OK with a wide variety of compression figures, I suppose if you fit a standard un machined head with the thickest gasket it could give the symptoms you describe. I reconned probably ten or more of the aforementioned Perkins engines. probably all with different compression ratios as a result of machining tolerances and they all ran but with different starting characteristics and noise levels.

There are other factors that can alter the compression even mor than the wrong thickness gasket, valve leakage and bore wear to name but a few, injection timing can also have a marked effect.

One problem the Perkins suffered from that I'm pleased to say the XUD doesn't is that if you set the pump timing over advanced, even a little, the crank shaft would break, I had it happen three times! I eventually got to know exactly how it should sound.

Peter

on a turbo charged engine its not a problem if its a small turbo boosting early on and the compression dropped a little boost can be increased whilst not increasing the charge temperature, giving increased performance whilst not harming the engine.
i have to say though ive never known it to cause a problem to the running of the engine unless the head has been skimmed to death and is u nfit for purpose.
Mind you i never skim heads anyway, unless the engine has been opverheated but after what ive learned in the last few weeks i will chuck any overheated heads, they become soft and fire ring failure is then almost garranteed (see my 'K-seal good bad') thread for photo evidence of what overheating does to alloy.

D