Broken Subframe mounting bolt R&R

[QSHIPQ at aol.com]

--
[ Picked text/plain from multipart/alternative ]
BTDT many times Dennis (in fact just a couple days ago to a 98 A4, so don't
feel bad:).  First, Monday morning QB:  The best way to get success on urq
subframe bolts is to heat them with a torch before removing them.  You MUST
replace the bolts afterwards (and the stinky melted SF bushings), since this
negates the 10.9 hardening.  A second way (later cars) is to find the frame
plug that allows you to soak the top of the bolt with rustbuster (do it a few
times in a week).  What causes them to fail is the subframe bolts usually go
thru the nut over a dozen threads, and they rust.

The trap nuts in the early audis are spot welded (man did they reslove that
in the later cars), and sit in a cage.  So either the cage deforms or the
spot welds break, lucky, sometimes both.

The fix:
Cut off the top of the bolt, and remove subframe/s.  The method I use is to
weld a nut to a really thick subframe washer (one of those 1/4in thick ones).
 Then I cut the top off the mounting post (urq) and weld the subrame washer
onto the mounting post.    Better than new.  The way a dealer or body shop is
instructed to do it (all chassis > present), is to cut a access hole (3 sided
box) in the side of the frame just above the nut, peel it open and R&R, then
weld up the box, put on new undercoating.  On the urq/80/90's this doesn't
reinforce a poor mount (which btw, audisport does on the rally cars, they
seam weld a thick reinforcing cap over the mounting post).

HTH

Scott Justusson
QSHIPQ Performance Tuning
'87 T44tqw mit RF repair
'84 urq LR/LF repair
'83 urq (heated and released)


In a message dated 9/21/02 7:37:03 PM Central Daylight Time,
martin at quattro.ca writes:


> I can't imagine I'm the first one to suffer such a failure. Anyone BTDT?
> How would a commercial garage handle this?

They cut a square hole in the body to gain access to the nut.
Afterwards weld it up and re-apply rust proofing.
I am not sure if there is any other way to fix this problem from the
outside.

BTDT on my 4kq.

Cheers
Martin Pajak