How to prevent cracking of RS2 EM ??

[S4-Sleden]

I just talked to a guy that is like a "multi-mechanic" at my job. He has alot of welding certificates and i talked to him about cracking of exhaust manifolds. He told me there is nothing with it.....i mentioned "glowing" the manifold in an oven but that wouldnt help he said because it is tensions in the material that does the cracking. But maybe some other in here have some other tips to prevent/delay the cracking ?? I know the exhaust manifold lives a hard life......glowing hot and cold again........glowing hot and cold again and so on and so on. I suppose i would crack myself being treated to those temperatures

[auditude]

Cryogenic treatment is purported to relieve those internal tensions that cause cracking. Maybe not all of the tension needed to prevent cracking, but that's something to look into. I've had it done to a 10vt 2-piece EM, but I haven't run that yet so I can't comment as to whether it prevents cracking.

Another option could be ceramic coating. My opinion is that coating the inside would be best, so that the heat is kept in the gas and not in the EM material. Some places do not coat the inside because it could flake off and potentially damage turbos and other downstream stuff. Those that don't coat the inside also say that internal coatings are not true ceramic coatings but are more of a paint which isn't as good as what they can apply to the outside. Some people coat the outside of their EM's, which seems more useful for corrosion protectoin than to prevent cracking. Seems to me it would hold the heat in and "cook" the EM more. But perhaps it's better than nothing because it may slow the change from one temp extreme to another.

If I were looking to do something to prevent cracking (which I am), I would look into the cryogenic treatment, at least by researching it if not trying it.

[iain1067]

Long time ago someone told me to have the face that goes onto the head skimmed so it's absolutely flat, this is supposed to stop it along with using the correct audi studs nuts and washers is also critical. How true the skimming part is i don't know, this came from a good freind of mine who has rebuilt many audi quattro ur.

[S4-Sleden]

What do you mean by "cryogenic treatment" then ?? Its dipped into liquid nitrogen ?? We have a HUGE tank of liquid nitrogen at work,maybe i can fill up a bucket and dip the EM in it ???

[AndersS2]

..and this is how a ceramic EM looks like:

[Corey]

On the 10v ur quattro this is a renowned weakness, the manifolds crack like ******y. We tested a cracked manifold on David Corfield's (Mint10valver) MB when it was in the workshop being rebuilt. It was nickle welded, so far 2 years down the line the manifold is holding up to David's daily abuse.
It is possible to repair but more cost effective to replace

[auditude]

What do you mean by "cryogenic treatment" then ?? Its dipped into liquid nitrogen ?? We have a HUGE tank of liquid nitrogen at work,maybe i can fill up a bucket and dip the EM in it ???

Check out some of these links from a Google search:

http://www.google.com/search?sourceid=navclient&ie=UTF-8&rls=GGLD,GGLD:2005-25,GGLD:en&q=cryogenic+treatment

It's a very controlled process. The materials are brought down to, say, 300 below zero, over a long period of time. Then they sit there for some prescribed period of time, and then are slowly brought back up to ambient. This converts some of the metal innards to different kinds of metal innards (much more technical description available from those sites, no doubt), so that there is more homogeneity in the metal, and stresses are relieved. It's supposed to make wear parts like rotors or toolling last longer, make brass wind instruments sound better, and make golf balls last longer, etc. It's everything you want it to be and more!

I had a K24, wastegate, and 10vt 2-piece EM done. Make sure you don't include any rubber or plastic bits with the parts, as they can easily come back brittle and broken. I did that with the wastegate diaphragm. I don't know if the turbo seals are affected by this, but I have heardn't read anywhere about special precautions for them. They did mine complete and just put the whole thing in there. It's a batch process, so if they have room in the "freezer", you can probably get a good deal on filling in the empty spaces. I've heard that they can do complete motors and subassemblies.

My cryogenically treated and ceramic coated 2-piece 10vt EM is still sitting on the MC-1 motor waiting to be installed into my Coupe GT, which has a slipping clutch. Good news is that I've fired that up to get the emissions tested to renew my registration. After it's renewed, I plan to swap in the motor so that I can get that out of the way and drive it while I delve into my other projects. The Coupe GT has been sitting so long that the fuel is old and I think it caused me to fail the emissions test twice. The first time I thought it was due to the timing being too far advanced over stock (pick either emissions or power), but after correcting that and failing again I'm looking to burn up the old gas, refuel, change the oil, and try again. Anyway, after I do all that I can report back about whether the treatment and coating prevented cracks.

[Mihnea]

If there's a heatshield missing on the driver's side engine mount, the manifold won't hold for very very long... no matter with what you weld it

That only applies for 10v turbo cars.

On the 10v ur quattro this is a renowned weakness, the manifolds crack like ******y. We tested a cracked manifold on David Corfield's (Mint10valver) MB when it was in the workshop being rebuilt. It was nickle welded, so far 2 years down the line the manifold is holding up to David's daily abuse.
It is possible to repair but more cost effective to replace