Re: exhaust manifold stud replacement

[steveb@falcon.kla-tencor.com (Steven Buchholz)]

> When checking the exhaust manifold studs re the exhaust leak there I found 
> fully 7 studs were sheared off. (New record perhaps?)
> So as recommended by this list the intake manifold, turbo,wastegate etc will 
> come off to see if the studs can be drilled in situ or else the head will come 
> off.
> Those who have drilled in situ (dremel tool I remember) are there any special 
> thinks to be careful of?
> It was suggested that I machine the manifold for flatness, any specs? or other 
> work do do while machining?!...
> If I have to remove the head is there any special R&R I should do while it is 
> off? Is there anything I should check on the turbo etc.  The car has 305,000 

I have had to deal with this myself some time ago.  My experience was that 
having the manifolds removed made it fairly easy to access the foreward 
studs and remove them pretty easily.  The problem is if you have broken 
studs near the rear of the engine.  I had a drill with a right angle 
drive and I still messed up because I did not drill the hole axis parallel 
to the stud's axis.  If you break off the extractor in the stud it is a 
pretty big deal ... led to my pulling the head.  Once I did that I found 
the cracks in the head between the intake and exhaust valve seats.  Bentley 
states that cracks smaller than a certain size are OK (FYI).  

Since then I found a set of extractors that had an integral drill (Alden 
Corp?) ... but I have yet to try them out.

I did have my exhaust manifold machined and the results have been favorable 
(no problems in 8 years).  Unfortunately I took the EM to a shop that did 
the dealer's work, so I didn't give them any flatness specs, I just asked 
them to do what they did for the dealer!  Perhaps you can talk to the folks 
at the machine shop to determine a reasonable specification.  

HTH!
Steve Buchholz
s_buchho@kla.com
San Jose, CA (USA)