Cylinder head reconditioning and gasket replacements 1.9 DG

[Mohamster]

I've had a diagnoses of head gasket failure on my van (1984, 1.9 DG). The coolant level was dropping and there were no leak, AA did a test with that involved a colour change showing that there were combustion gases in the exhaust.

My plan now is to remove the engine then replace the water jacket seals, cylinder gaskets and also all the bolts. I've seen conflicting advice whether or not to have the heads skimmed before reassembling (bear in mind the engine has not overheated, so I'm not expecting any warping), with some saying it's irrelevant. Any definitive answer to this?

Many thanks in advance

[ajsimmo]

No skimming needed. These heads don't quite work that way. Look for any sign of someone previously gouging a chunk out whilst trying to remove a compression seal, and that could be the cause of the failure. More often, they were not assembled/torqued correctly, or maybe they just used rubbish cheap (or re-used old) gaskets.
If there's a sign of leakage on the head eg a dark track where gasses have been escaping, then bingo! You've found the cause, and a light lap with a barrel will show if it's flat or warped/damaged. New good quality (Elring/Reinz) head seals will sort it.

[Mohamster]

Thanks for your quick and informative response! Could I just check with you, what do you mean by a "lap with a barrel".

Also, I'm planning on replacing all the cylinder bolts to make sure that I'm applying the right torque and to forestall any bolt failure by corrosion (will be renewing the coolant and keeping a regular replacement schedule) .. this isn't overkill is it?

Many thanks again!

[itchyfeet]

To properly clean up the mating surfaces in the head and on the crankcase and barrels takes many hours.
My guess is many people just don't put enough effort in.

Another possability is that the green oring didn't seal well and the combustion chamber seal has corroded, often heads will stick to barrels if corroded and may have been damaged when seperated.

I thinjk Ajsimmo means use a barrel perhaps with some fine grinding paste to lap the head mating surface, never done it myself but sounds a good idea.

[itchyfeet]

BTW they are studs not bolts and if in good condition I'd leave them

[ajsimmo]

Hmm...good luck with replacing the studs (not bolts) - it can be a very difficult task, and beyond the scope of most amateur mechanics. The whole case will usually need splitting and stripping down, then baking in a hot oven to get enough heat in there to persuade the studs to come undone. Some may break in the process, and if broken off near or flush at the bottom they'll need drilling out and machining/helicoiling.
Or you may find the world is perfect that day, they all come undone with ease, whilst everyone has a big smile, bluebirds are singing around you, and your fantasy partner turns up in a skimpy outfit with unlimited cups of tea and a packet of hobnobs. Or they might not...be prepared for the former scenario whilst hoping for the latter!

As for lapping in, well on some Aircooled heads they don't use the metal sealing rings any more, so instead you make sure you have a flat sealing face (of barrel to head) by putting a little valve grinding paste on the mating surfaces, inserting the barrel and gently turning it back and forth between your hands. It's like lapping a valve into it's seat, but bigger. So doing this on a WBX head effectively means both the head and barrel face are as good as they need to be to give a perfect seal when the ring is used.

[ajsimmo]

Ah, I see I was beaten to it by Mr Feet whilst typing, so WHS^^^

[Mohamster]

Thanks Itchyfeet ... I've been consulting your posts on engine reconditioning in preparation.

Also, thanks AjSImmo for the terminology explanation of lapping. Makes more sense to my green self now. Good tips about the studs, didn't realise it was so involved fingers crossed there's no corrosion/wear and they can just stay in

Hopefully this all goes well and no more questions from yours truly .. but unlikely!

[CovKid]

You should find these useful too if you find much pitting of rubber seal area of cylinder heads:

https://www.youtube.com/watch?v=bChepZkJfbk" onclick="window.open(this.href);return false;

https://www.youtube.com/watch?v=P9r_aJ0Mp50" onclick="window.open(this.href);return false;

Ken Wilford's Youtube channel is excellent too. He's an 80-90 member.

https://www.youtube.com/user/kenwilfy/videos" onclick="window.open(this.href);return false;

[Mohamster]

Many thanks to all for the replies and advice! The videos are very useful.

Quick question:

I don't know whether it is one, or both of the cylinder gaskets that have failed .. should I just be safe and change both sides? I'm assuming that once I've opened that it will be time to change anyway and don't want to only change one side only for the other to fail or be close to failure.

Thanks in advance

[itchyfeet]

I would do both sides and I would remove the engine to do it.
I would remove pistons and barrels together and change the lower liner seals, proper job.
Hard to work on it in the van much easier removed IMO.
There is extra risk however of snapping studs if you do both sides.

[Mohamster]

Hello there, so finally got the engine out of the van and the moment of truth came. Both heads came off without
much hassle

Good bits: no sign of cracks between valves and not much pitting in the rubber seal area

Onto the bad bits followed by some queries. Link is to Dropbox folder of pictures of issues, I couldn't upload pics

https://www.dropbox.com/sh/x6irfjrnlvbe ... KK-Sa?dl=0" onclick="window.open(this.href);return false;

Bad bits:
1- a scratch under one of the compression rings and some really weird scratch pattern on another (I've attached some pictures showing it. Is this where the lapping comes in to fix this?

2- the barrel (piston liner?) did stick to the head but I kept in place using advice from Kenneth Wilford vid . Seems there's a fair bit of corrosion on the barrel mating surface so my guess is the green o ring has failed (it's not
Got O profile any more but also perhaps part of
Failure Down to the scratches on a couple of the mating surfaces .

So,I'm wondering what next.
1-Does this damage look repairable with some
Sort of liquid metal type product or could a machinist skim me a new mating surface? My long term game plan is to get AMC heads (who supplies these?) but I can't afford at the moment.
2- Secondary question about removing barrels to clean. Is this actual possible one at a time without having to rebuild the whole piston ring assembly?

Apologies for the waffle and thanks in advance

[Oldiebut goodie]

Looks like burning to me.

[Mohamster]

Looks like burning to me.

Hi OldieBut Goodie ... Thanks for the assessment. It's somewhat rough to touch if that helps. What does this mean in terms of the usability of my cylinder head? Pardon the stupid question ... Engine overhaul noob in
Da house

[Oldiebut goodie]

You will have to wait for one of the petrol guys - I know nothing about those funny engines, , and what could be done. It all depends upon how deep they go I should think - it seems fairly bad to me without physically judging it.