Head Gasket/Skimming

[RJE]

Hi guys, bet you get bored of questions about head gaskets but hope you can help here.
I bought a 02 MGTF 160 VVC at the end of June from an independant dealer and as part of the deal they replaced the head gasket because I knew these were particulary weak on this model of car.
Now, 1500 miles later the headgasket has failed which Im not too pleased about. It sounds me to me like the dealer never replaced it in the first place or it wasnt done properly for it to fail after such little mileage. Fortunatly the car is still covered by the dealer warranty.
Now the real Q, the dealer informed me that when the headgasket was supposedly replaced before the head would also have been skimmed, but then I have been informed from another source that heads on TF should never be skimmed. Could someone tell me which is the case?


Many Thanks.

[Chris Tideswell]

The head should only be skimmed if needed, i.e. if the head has warped, if the was found to have not warped then it should be left alone as skimming has it's own risks but the procedure can be used to save the head if needed. The problem is that the second time there may not be enough left to skim meaning a new head is needed.

[Stampy]

As Chis said, the head only needs skimming if the gasket fails and allows the engine to overheat.

If the alloy head gets too hot it warps, so when it's put back together the mating face doesn't sit flush on the gasket and leads to further problems........as yours was "replaced" as a precautionary measure I'd be inclined to say they had no need to skim it

[iaross]

Just watch out the garage doesn't do a DIY skim with a rotary sander as happened to me!!

[mel123]

Err.....no expert but i got told that it should be skimmed and pressure tested as a matter of course after hgf. It would depend on how much the head was skimmed the first time as to weather it will take another skim.
My 1997 mgf has had the head skimmed twice. The first time i,ve no idea by how much. The second time by six thou. I was reliably informed at the time that the mgf 1.8 k series head has been seen in good service after having up to a mil skimmed off.
If you want to look into it further i would suggest you type "dave andrews" into google who knows and modifies the k series head.
The condition and the hardnes of the head needs to be looked at aswell before a decession can be made on wether to skim it or not.
Also get the latest LR gasket.
Hope this helps
Mel

[sniperpenguin]

Now the real Q, the dealer informed me that when the headgasket was supposedly replaced before the head would also have been skimmed, but then I have been informed from another source that heads on TF should never be skimmed. Could someone tell me which is the case?

Both are wrong. You pressure test the head - if it fails, you skim it then test again. If it fails, the head is usually knackered.

Replacing the gasket on an 02 car is pointless unless you are changing it for a better gasket (e.g. the Land Rover one), since the fault lies with the head itself You want to completely remove the "2002 curse"? change the head for a new one / non-2002 reconditioned one.

Hope this helps.

[Geoff.F]

The head is Pressure Tested to check for porosity. No amount of machining can remove this.
Geoff F.

[mel123]

The head is Pressure Tested to check for porosity. No amount of machining can remove this.
Geoff F.

Geoff how does this pressure test work then to check for porosity .
I thought the pressure test was to see if it was machined flat after/before the skimming.
Would just like to learn abit more
Mel

[mgtfnut]

The head is Pressure Tested to check for porosity. No amount of machining can remove this.
Geoff F.

Absolutely right. Skimming is only "necessary" if the head is warped after severe overheating. It may not need skimming at all.
Worse still is the softening of the alloy which may lead to liner marking/sealing problems of the head, no matter how many times you skim it. This is sometimes over looked. A hardness test should be made on the cylinder head surface.
Porosity is something completely different, and may have been there since day one. A chance skim may remove it - unlikely, and the LR gasket might possibly do something to help here. Normal porosity means a new head.
A pressure test is just that, a pressure test to see if the combustion chamber and passages hold up when pressurised. If porous, leakage will provide evidence the head is probably scrap.

[mel123]

Cheers for that
The reason why i,m asking is that a mate of mine got his HG done at a VERY well known garage and they said that skimming should be done as a matter of course as the head may not resume it,s original position /trueness when re fitted,so they always skim the head after a hgf.
I will check the above next week .
What i,m thinking is that i,ve had my hg done last year and the previous owner had it done 4 years earlier. I got the pressure test and skim (all ok)and the lr gasket, so my head would probably not take another skim. If it went again......what would you do providing the pressure test was ok,just re fit a new gasket??
Just want to arm myself with the right choice now if i can.
Cheers guys

[Debs]

Bah!

Most garages will insist on skimming.

Why?

Because they know DAMN ALL about the K Series!

The Ally that the K Series is made from is case hardened via quenching - is why the engine is so light - overheat it and you destroy the case hardening.

Now, if you skim the head you remove the case hardening.

SO...

UNLESS you use a multi shim gasket after this, then you are highly likely to get gasket failure again.

[MGsteveT]

Debs has got it spot on!
I could'nt have written it better myself.