Head Gaskets - 1,2,3 or No Hole

I've just found out my Tdi problem - blown a head gasket between cylinder no's 2 & 3. The head Gasket i've removed doesnot have any holes to identify the thickness. I've recently been told that this gasket is 1.69mm thick and 1 hole is 1.3mm, 2 hole is 1.4mm and 3 hole 1.5mm. I've had to get the head skimmed and have been told to fit the same size gasket (1.69mm). Does anyoneknow this to be right ?? Any comments as to wether this is ok ???

I'm not one for saying 'I told you so....' but I do sympathise. Mine went a few weeks ago, on number 4 (the usual place) but luckily I didn't have to have the head skimmed.

Ask the company that skimmed your head to let you know how much they took off. Check with your local LR parts agent which gasket would NORMALLY fit your engine (you'll need your VIN number).

If your engine normally takes the 1 hole gasket and the head has been skimmed by 0.39mm, then 1.69 should be OK.

Someone may be along with a better explanation, but that's what I would do.

You need to measure the piston protusion,ie how much each piston sticks up above the block face when at TDC. There is a chart in the W/S manual that will tell you which gasket to use.The head face is flat so how much you remove from it makes no difference to gasket thickness.

The head face isn't flat if it is warped. Once you skim the head surface, you remove a certain amount of material which lessens the space that the piston can travel into, hence the need to put back that original 'space', by adding a thicker gasket.

tonyw said:

The head face isn't flat if it is warped. Once you skim the head surface, you remove a certain amount of material which lessens the space that the piston can travel into, hence the need to put back that original 'space', by adding a thicker gasket.

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Dont talk cr-p, the bump clearance is set by the thickness of the gasket.The pistons protude above the deck face,and the combustion chambers are in the piston crowns. Read the book and you will see what I'm dribbling on about.Lots of garages just put the thickest gasket on as there should be no chance of piston to cyl head contact - unless the deck face gets machined.Like most of its proceedures it is quite clearly laid out in the LR workshop manual - trouble is most people cant be bothered to read them.

eightinavee said:

Dont talk cr-p, the bump clearance is set by the thickness of the gasket.The pistons protude above the deck face,and the combustion chambers are in the piston crowns. Read the book and you will see what I'm dribbling on about.Lots of garages just put the thickest gasket on as there should be no chance of piston to cyl head contact - unless the deck face gets machined.Like most of its proceedures it is quite clearly laid out in the LR workshop manual - trouble is most people cant be bothered to read them.

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Look at my previous 2 posts again, but try it from a different perspective. As I see it, what you have written is what I have tried to put across, albeit badely. I think a novice would understand my version better than yours, and a novice is what I be. At least, I understand my version more than yours, but even I can see that they basically say the same.

I DID say that "someone may be along with a better explanation".

if you skim the head you increase the compression ratio.
sometimes desirable, sometimes not.
there is also a piston/valve clearance problem for some injuns. im not sure how much you can safely remove from a 300tdi head.
but you do need to check.

when we rebuilt rally engines, we always turned them over by hand first to check. just in case we got the sums wrong!

You still dont get it do you ? The head face of a TDI is FLAT,so it does not matter if you skim it,its the thickness of the gasket that controls the bump clearance.The only area of the head face that doesnt get skimmed is the small area around the valve heads.There is a limit to what can be safely skimmed off the head,plus the measurement of the valve faces to head face needs checking and material removed from the valve seats if the measurement is too small.
The Head Gasket is chosen as a result of checking against the chart with the height of the highest piston protusion measurement.This should be checked every time the head is taken off,so you dont rely on the last bloke getting it right.The only time a different thickness gasket is used is if new pistons/rods/crank is fitted or if the block face is machined.
The gasket choice is as follows,
Protusion 0.50 - 0.60mm use a 1 hole gasket
Protusion 0.61 - 0.70mm use a 2 hole gasket
Protusion 0.71 - 0.80mm use a 3 hole gasket
Protusion 0.81 - 0.90mm use a gasket with no holes.
The protusion is best measured with a DTI,but can be done with a straight edge and feeler gauges.
So gasket choice is nothing to do with head skimming,hope this is more clear.Remember this is a diesel,lots of diesel procedures are very different to petrol engines where most of them have the combustion chamber in the head face,so skimming raises compression - hence needing a thicker gasket to keep the compression ratio the same and maintain valve to piston clearance measurements.

I agree with the last comments, had my head skimmed but another problem has come about... cylinders no 2 and 4, the hole where the glow plug comes through on the combustion face there's a tiny crack. Also between the valve seats on the same cylinders theres a crack on the aluminium part between them and the hole where the injector comes through.... S**T! The cracks only travel up the holes approx 3mm and don't go right through to the inside of the valve chamber, couldn't see these prior to getting the head skimmed... New Head I think...?

eightinavee is correct with his last comment, the tdi head is flat, it dosent matter how much you skim it , its the protrusion of the pistons above the block line that determins the thickness of a gasket, but id put a three hole one on, (thikest).

Here's the Picture of the cracks, the second is to the left of the glow plug hole.. Has anyone seen this before or had any experience with this problem..????