[urq] 2-Piece Manifold

[urq]

I did have a chance to talk to Javad about this the other day ... he echoed
the other comment we heard here, that EMs are difficult to weld.  He also
commented that a crack doesn't necessarily mean a leak.  I also talked to
him about cryo treatment and thermal barrier coatings.  He said that he
never heard much about people doing the cryo treatment, but did believe
there was value to thermal coating on the inside of the EM.  Such a
treatment keeps heat out of the manifold, allows more energy in the exhaust
to get to the turbo and works to minimize under hood temps.  I'm also
thinking that a thermal coating might also tend to seal any small cracks
that might be present.  

I'm planning to have that new 2-piece I have coated on the inner surfaces
before installing.  

Steve Buchholz

OBTW, the food from the MoGo BBQ catering truck was pretty doggone good too!
Javad rolled out an A4 race car to drool on while we ate ...

-----Original Message-----

I think Justy reported that the 2-piece manifolds can crack a while ago.
The cracks inside the manifold occur in the one piece as well, and Audi
claims these do not pose a problem.  This is plausible because any "leaks"
would remain inside the exhaust system.  

I found similar external cracks on that previously uncracked and resurfaced
manifold that was on my car before the MC went in.  It almost seems that
cracks are inevitable.  I had the head on my WX welded to repair cracks,
perhaps this is what needs to be done with the EMs.  

I'm going to Javad's tomorrow for lunch ... I think I'm going to ask him for
his thoughts on the subject.  

I still have a brand shiny new 2-piece EM in the garage.  My plan was to
have the part cryo-treated and thermal coated on the inside before it ever
sees action ... 

As to the igloo ... it has been a while, but I'm pretty sure the brass
insert is just pressed in.  On my car one of the hoses comes off with the
brass!  I would try to drill out whatever is left of the brass in the
casting and reinsert a piece of brass tube, perhaps with some JB Weld to
hold it in place.  

Steve Buchholz

-----Original Message-----

I haven't driven my car much in the past year. Anyone who's heard it run
lately can identify the distinct sound of exhaust gases successfully
escaping their manifoldly confines. It has a two-piece manifold, but the
leak is obviously coming from its vicinity. I pulled it last weekend to find
the source... 



I found four obvious cracks: two on the underside, and two more in the
dividers at the turbo end. I also found evidence of significant exhaust
escaping around the #1 port and its predominantly AWOL gasket, and maybe a
hint around #2 and #3 ports. We think at least one of the nuts on #1 wasn't
as tight as it should've been. Due to the volume of the leak, I suspect the
#1 port is the main source. Here are some pictures of the manifold in
question: 

http://home.comcast.net/~racingiron/ExMan/manifold1.jpg 
http://home.comcast.net/~racingiron/ExMan/manifold3.jpg 
http://home.comcast.net/~racingiron/ExMan/manifold4.jpg 
http://home.comcast.net/~racingiron/ExMan/turbo1.jpg 
http://home.comcast.net/~racingiron/ExMan/turbo2.jpg 

Removal (with head in situ) wasn't fun, but better than I expected. Only two
studs refused to be divorced from their nuts, preferring to separate from
the head instead. Unfortunately, the lower #2 stud apparently harbored
strong attraction for the head as well, retaining bits of it in about half
the threads. My German cohort (with not insignificant MB surgical experience
in the Fatherland) thinks I might be able to get away with a simple retap
(or rather, chasing with 3 progressively aggressive taps), while I'm leaning
towards a helicoil-type repair. The #2 location seems to lend itself to
drill application with the airbox and turbo conveniently out of the way. 

So, my questions: 
- Fix or replace the manifold? The cracks in the collector seem unlikely to
be easily repaired. How tough is it to find a good 2-piece replacement these
days? 
- Advice on the lower #2 stud threads in the head? Tap? Helicoil? Time-sert?

- Oh yeah, we snapped one of the brass barbs on the CIS intake dome. Is
there an reasonable fix for this, or should I just cap that hole and put a
tee on the second one? 

TIA, 
Eric R. 

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