RE: cracked 2-piece manifold for MC...

["Buchholz, Steven" <Steven.Buchholz@kla-tencor.com>]

Well, on my '88 5kCSQA the exhaust system and motor mounts are all in fine
shape, AFAIK they've never been replaced either.  When I pulled the EM to
have it resurfaced (which is all that I needed to do when I did the ur-q
years ago) the shop that was going to do the work showed me a couple very
small cracks in the EM near where the #4 and #5 runners connect to the main
collector ... fortunately I had procured an EM without cracks from a qlister
as insurance ...

While I would agree with a statement that broken studs can be correlated to
motor mount and/or exhaust system stresses, I'm not so sure I've bought into
this causing the cracks ...

Steve Buchholz
San Jose, CA (USA)

> -----Original Message-----
> 
> << I am slowly becoming _convinced_ that manifold cracking is largely
>  caused by failing motor mounts, especially the one directly under the
>  turbo. >>
> 
>     I definitely agree.  Imagine the force of the entire 
> exhaust system 
> constantly wrenching back and forth on the manifold, must be 
> very hard on it. 
>  I have found that the problem is exaggerated when the 
> mounting point for the 
> down pipe has been removed,  putting all the stresses on the 
> manifold.  
>     I think that the drivers side motor mount is especially 
> critical since 
> the motor is pulling up on that mount.  If that one happens 
> to break, the 
> motor really bounces around.  In my experience, I have never seen the 
> passenger side mount fail, it is always the drivers side 
> since it takes most 
> of the abuse, IME...