RE: Violent Back-off - Testing Motor and Transmission Mounts

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

> How do you test motor and transmission mounts?  Is it just a 
> visual check,
> or can you give it some kind of operational test?  What am I 
> looking for?
> 
What kind of car do you have?  Many times the cars with the hydraulic mounts
are obvious ... you can feel that the rubber has hardened and cracked around
the periphery.  The "hot" side mount on my QTC was so bad that the rubber
had started to disintegrate, and the oil pan was contacting the front
subframe in some situations under acceleration.  Some newer mounts have a
"cover" of sorts on the top that I would imagine is there to help keep the
heat away.  My '88 5kCSQA is this way ... I check the mounts by probing
underneath the cover with my hands ... since the rubber still feels pretty
supple and not cracked I've assumed that they're OK.  

Some of the other non-hydraulic mounts are difficult to check out without
disassembly.  The tranny mounts on the '80s quattro models are this way as
well.  Many times simply looking at the mounts they seem like they are OK
... but when you take the mount off it falls apart in your hand ...

Another bad thing for an engine mount is if it has been exposed to oil,
hydraulic fluid, brake fluid, etc. for some amount of time ... it can cause
the rubber to decompose ...

If you have a type 44 turbo, I highly recommend making sure that the
ductwork that provides cool air for the right motor mount is all in place
...

HTH!
Steve Buchholz
San Jose, CA (USA)