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MonsterL35YFP

Hello polo people, I have recently changed the head gasket on my mk2f coupe and after being ran up a grand total of 4 times oil has started to seep from under the gasket just above the alternator, iv had the head skimmed and cleaned up the block surface did everything by the Haynes manual, anyone got any suggestions what iv done wrong? 

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yeah fit a set of valve stem seals while its off...idealy lapping the valves in at the same time

One or two head gasket tips - most have already been covered in the above replies though. It is very important that the threads in the cylinder block are clean and dry - I have seen cylinder bloc

steveo3002

did you use new bolts ?

 

reasonable quality torque wrench thats never been abused? and did you do the +  xx degrees properly?

 

i had one leak - no idea what i did wrong and in desperation i cracked the bolts round a few more degrees , fixed it and i ran the car for years with no further trouble

 

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MonsterL35YFP

I used a brand new draper torque wrench and I'm not going to lie but me and my brother (who's done plenty of head gaskets) did the angle torque down by eye, iv spoken to my dad (retired mechanic) and he reckons could maybe doing with another 45° turn all round 

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steveo3002

yeah worked for me , theres the slight chance a bolt might snap though , guess i did mine about hour n half on a clock face 

 

were the bolts branded?  ...get so much rubbish these days  

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kwijibo_coupe

Common spot for oil to leak really.

I've heard of people giving the bolts an extra little turn which sorts it.

Or the method I went for is a thin smear of anaerobic sealer on that section of the head gasket, but since you've done the job now that would require doing it all again.

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steveo3002

one other thing to check in the future....clean all the head bolt holes well , if theres oil or water in them then the bolt wont compress it and ruin the job

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MonsterL35YFP

The head bolts are febi brand, Iv tapped and cleaned the block holes, dipped the bolts in copper greace before torque down.

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steveo3002

not sure you should have greased them ...will effect the rating 

 

anyway...its a choice of take the chance and pinch them up a bit more or start over again with new parts

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MonsterL35YFP

Well I nipped my head bolts up another quarter turn they didn't feel overly tight at all and made no difference still leaking oil so iv brought new head bolts I'm thinking they must be the wrong ones or faulty. 

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steveo3002

are you fitting a new gasket?

 

id say it takes a reasonble amount of grunt to get them to spec...something is wrong is they dont feel tight

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MonsterL35YFP

There tight but not to the point where I'm really struggling to turn them and I was just thinking about replacing the bolts not the gasket but I might take the head off and see what's going on. 

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kiran_182

Best to do the gasket too as it deforms under pressure and adds an extra risk you dont need

 

Edited by kiran_182
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dvderlm

And clean the bolt holes and do not use copper grease. The bolts need friction to stretch not anti-seize lubricant.!

Any torque wrench reading with grease would be off.

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kiran_182

Wheve had a few hg threads and lots of decent tips, any chance a mod can pull all fhe info into one thread

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MonsterL35YFP

Ok guys well iv ordered new head bolts and a new head gasket and start again, stripped all the necessary ancillarys off the head while doing so noticed that cylinder 1 is burning alot of oil or has been at least.

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steveo3002

yeah fit a set of valve stem seals while its off...idealy lapping the valves in at the same time

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MonsterL35YFP

When I had the head skimmed, I had new valve guides, values cut and seated and I replaced the valve stem seals so it's either a piston ring or oil is leaking into the cylinder because of the head gasket 

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caretakerplus

One or two head gasket tips - most have already been covered in the above replies though.

It is very important that the threads in the cylinder block are clean and dry - I have seen cylinder blocks crack due to the hydraulic effect of leaving oil or coolant in the bolt holes.

The only thing that prevents the bolts from coming loose, is that fact that when they are tightened, they stretch - just like elastic!

When the bolts are slackened off, they return to their original length - again, like elastic.

Just like elastic, if they are over stretched, they may not return to their original length, continued overtightening will cause a waisting effect on the bolt, known as 'necking'

It is vitally important that at least the original tensile specification is used for any replacement bolts - hence the advice to use genuine VW bolts (Others are fine, IF you know that the specification is correct)

If an engine manufacturer specifies lubrication of the threads, then they should be lightly lubricated. However, most manufacturers recommend dry threads. Obviously, if threads are lubricated, when they shouldn't be, and the correct torque (which relies on friction) is applied, the bolt is likely to be over stretched.

The area where these gaskets leak from, is always just above the alternator mounting, the drilling there is the main oil feed to the camshaft, so is always under full oil pressure. Thnat is why you have been given advice (above) to use a SMALL amount of anaerobic sealer on that area of the gasket ONLY.

It is normal to start tightening the bolts from the centre, working outwards (It's a bit like wallpapering - it squeezes out all of the bubbles) - Always work in stages, starting with JUST over finger tight, working up to the full torque and then the CORRECT angular movement (where applicable.)

I always find that it helps to count the bolts as you tighten - that way, when you reach the last one, you should have counted the complete number of bolts - proving to yourself that you haven't missed one'/done one twice.

It isn't possible to check the torque of any bolt/nut simply by re-applying the torque wrench - This is because the correct torque is reached DURING turning, so 'checking' from stationary would give false results.

If you don't have an ENGINEERS straight edge or a surface plate, you can check if a block or head face is warped by applying a VERY thin layer of Mechanic's Blue (Engineer's Blue is an alternative name) (this is available from engineers merchants) to one side of a piece of PLATE glass (from a glass merchant) and rubbing it back and forth over the head or block surface -  the blue will transfer onto high areas of the block/head face, leaving any low areas 'bare.'

NB Only use plate glass for this 'normal' (float glass) may not be flat enough.

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MonsterL35YFP

Cheers for the info guys I'm having abit of trouble sourcing the right head bolts at the moment order some and they've come at 98mm long 

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MonsterL35YFP

I'm going to take the back to euro car parts and see if they can get me the right ones if not I'll be going elsewhere 

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kwijibo_coupe

Aren't the 98mm long bolts the G40 head gasket bolts? 

But regardless that wouldn't effect the torque unless they are bottoming out.

Also I assume you're going through the angle tightening sequence after the torque tightening? As that is the point where the bolts stretch.

Unless you're using a standard half inch ratchet, doing the angle tightening sequence shouldn't be too much of a physical effort, but it should feel like you're doing something. 

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MonsterL35YFP

Well according to the internet they are for PY/G40 engine but only rated at 8.8 so must be for the later 8v engines, i did it all today it looks to me some excess oil left over from when I was cleaning the pistons was around the piston rings and just sat in the cylinder so cleaned it all out she's running like a dream after slightly adjusting the dizzy so I'll see how I get on but everything seems good, cheers for all your help chaps.

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