Turbo to manifold mating surface! Question.

[shox75]

How can i ensure a good seal like fromt factory? Anybody make a custom gasket? Or just clean it up, and once engine heats up the seal will be made?

[fspGTD]

The factory sealing is just two flat and smooth surfaces that should be leak-free when bolted up.  However it is possible for it to leak I'd imagine on old turbos and exhaust manifolds due to corrosion.  The "by the book" way to restore the seal on these surfaces is by machining them flat if they are badly rust pitted or warped.  The problem is all the hassle to get the parts removed and machined and the associated costs.  Unfortunately, there is currently no available gasket for this application available in the aftermarket.

However, I made a one-off custom gasket out of copper for mine that I'll be testing when I get my GTD autocrosser up and running.  I'm sure it will cure any possible sealing issues there may be with the old, somewhat pitted sealing surfaces just as well, but the main reason I made it was to space the turbo away and get adequate clearance from a custom intake manifold I'm making.  Below shows a picture of it taken from this thread: http://www.vwdiesel.net/phpBB/viewtopic.php?t=614&start=63



I could have used stainless instead probably just as well, but I decided to use soft copper to add help with the turbine flange sealing.  Soft, annealed copper is a good material for this and is sometimes used to seal head gaskets and other difficult appliations.

If you and enough others are interested in a thinner version of my copper gasket, designed specifically to ensure a good pre-turbine seal (not a bad idea for old, pitted sealing surfaces, especially if you're planning on running lots of boost, it could only help and certainly would be overall cheaper and easier than taking the parts to a machinist to have them flattened), I would consider making a run of them and offering them for sale.  If you are interested, please send me an IM or e-mail.  Thanks.

[935racer]

There shouldn't be too much corrosion between the turbo and manifold unless they were sitting separated for a some period of time. I have never seen an exhaust leak between the manifold and the turbo before ont his cars but I wouldn't rule it out from being possible. As long as the surface isn't noticably pitted or anything I wouldn't worry about it. Jake thats a pretty snazzy gasket  good call on the copper thats exactly what I would have done. Running more boost shouldn't affect the seal between the turbo and the manifold though.

[fspGTD]

Dave - I'm curious how you tested the seal of your turbine inlet flange.  It would probably take a pretty large leak and by that time performance could have suffered pretty badly before the driver noticed the poor performance and exhaust leak ticking sounds enough address.  Seems to me that small leaks the driver might not notice especially if they develop slowly and gradually, would be pretty difficult detect.

I think you might be surprised at how warped the flanges can actually get.  The high spots can be discovered by rubbing the surface carefully with a flat file.  (just be careful to keep the file oriented flatly so the edges don't dig in, and also be mindful of where you are putting your metal shavings!)

When I first tested the flatness of my exhaust housing turbine inlet flange a few years ago and then restored it to flat, the edges of the flange were initially raised up quite a bit more than the area closer to the inside.  I very carefully filed it as close to flat as I could get it. (no easy task, even with the widest flat file I could find.)  And now with the turbo removed again and the head off the car, inspecting things it looks as if the warped surface has returned!  

I think there's a reason why all-out race motors often are build around "seasoned" blocks instead of fresh castings - the cast metal can simply move around after being repeatedly stressed and heat cycled.

[935racer]

Jake there is this high temp form a gasket stuff. Its great, just smear a bit around the mating surfaces and go take her for a boot and get it nice and warm, than inspect for any areas where it looks like the sealer came apart. I don't think it is strong enough to hold any gas in but heck if it is than thats great too cause than I know its not leaking!

[fspGTD]

Figuring that some copper anti-seize might be able to take the heat and could possibly help the seal, I have tried smearing some of that on before.  It didn't seem to help anything and apparently just got blown out.  On the next disassembly there was mostly just carbon deposits.  :x

[935racer]

Sorry let me clarify, I put the goop on when the turbo is installed. I just smear some around where the turbo and manifold mate, and to date theres been no leaking fate.