pre chambers not flush

[moTthediesel]

So I'm working on the head of my mechanical lifter 1.6TD engine. Everything looks fine, no cracks that I can see and it checks out nice and flat. The exhaust valve guides were worn almost to tolerance (about .045") so I replaced all the guides.

What does bother me though is the pre chambers. While they are not cracked, they are no longer flush with the head. They are flush in the area where they bear on the engine block, but they are standing proud of the head about .010 in the area diagonally opposite that. I have searched here and have seen a good bit about cracked chambers, but I've seen no mention of this particular problem.    :?:

Has anyone here seen this before, and do you see it as a major problem? With no cracking apparent, it doesn't seem likely that cause any real threat to damage the engine, but it still causes some concern for me.

moT

[jimfoo]

I'd worry about it getting worse as that's about 1/3 to 1/2 the distance to hitting the piston, at which point all hell brakes loose. Who knows, maybe that's what happened to mine. I have no clue as to the cause, but can speculate about the head getting hot.

[moTthediesel]

I would peen them in place.  Having one fall out into the cylinder is not unheard of and causes a very bad day.

Andrew

Ugh, I sure don't like the sound of that  :shock:

I've never seen a VW pre cup out, how deep do they project into the head? The only ones I've changed were on my LandCruiser, and they went a full 3/4" or so inside, very secure --

moT

[moTthediesel]

Looking at the head again, what I see is that the pre cups are clearly deformed. The section of the cup that is covered by the head (just less than half it's area) is perfectly flush, the part inside the combustion chamber has "bent" down. Makes me wonder if they are cracked on the top side where they can't be seen?

Perhaps I should drive one out with a drift down through the injector socket so that it can be examined?

moT

[CoolAirVw]

Perhaps I should drive one out with a drift down through the injector socket so that it can be examined?

Better do something.



see this thread

http://www.vwdieselparts.com/forum/viewtopic.php?t=7799&highlight=

[RabbitJockey]

wow i didn't know that could happen, kind of scary

[rallydiesel]

That's why a TDI conversion is so nice. No more pre-cups to worry about.

[moTthediesel]

Perhaps I should drive one out with a drift down through the injector socket so that it can be examined?

Better do something.

see this thread

http://www.vwdieselparts.com/forum/viewtopic.php?t=7799&highlight=

Thanks for that thread, scary, but helpful  :shock:

What were the rest of the cups in your head like? Interesting to me that all 4 of mine are exactly the same.

Not sure what I should do though --

Drive my cups out, install new ones, then peen? Where do I get cups? I don't think I've seen any parts places list them, and won't driving them out and pushing new ones in just make them looser?

Try to press the cups back to flush and then peen? Not sure that is do-able. Are they made of stainless steel or what?

Just peen the cups as they are now?

I do like the smooth ball peens shown in the pictures, much less likely to act as heat and stress risers than a sharp pin punch would be I think.

moT

[CoolAirVw]

I believe the pre-cups are inconel.

I would try tapping them back in and then peening.

Andrew

what he said.

[Patrick]

1.9 cups are available, don't think 1.6 cups are. IF you go that route, I think there's machining involved. I CAN tell you that if the cup breaks/comes loose, it WILL make a heck of a mess. Had one come out on a 1.6 and wreck a very good running engine. I've got 3 out of four good oversize pistons on the shelf........... THe fourth one looks like someone spent an hour or so hitting it with a chipping hammer. So does the head...............