HighPSI

should be strong enough to get it to spin, which'll dislodge it from whatever has seized it up..

OMG!!!!!one!!1!

Better hit up the dealership for an extra one in case you snap it

HighPSI

shouldnt snap, it'll either spin or it wont, or it'll strip it

s4wood

It could break...seen it happen..no..not by me

HighPSI

ok

s4wood

Let me first premise this by saying that I have been involved in over 35 suspension installs on B5/B6 A4/S4 cars...by saying involved..I mean I got paid for removing and installing another suspension on these cars. I have had my share of difficulty with that top bolt. Mostly, the issue has arisen on cars from the east..where salt is used in the winter months on the roads. Rust then develops more easily making suspension component changes much more difficult. So, with that being said, here are my suggestions:

1) Use WD40 vigorously
2) Try not to bang that bolt with a hammer any more..you are ruining it..and unless you got a spare from the dealership..you gotta use it again. To be honest..from the pic..you may have already ruined it..and may..I say may...have to hacksaw off the last several threads just to get that thing out.
3) Jack up the suspension with a hydraulic jack..to relieve pressure on that bolt.
4) Put a closed ended wrench on bolt head side of the bolt and move it up and down..while spraying it with more and more WD40.
5) Note: the use of a pry bar might be slightly effective between the suspension component and the bolt head..but this will only work for the initial loosening. Do not use a pry bar in between the two spots just below where the upper control arms go down. The upper control arms cannot be removed without removing that bolt you are having trouble with..so don't force them out.
6) Do not use air tools on it at this point..too hard to control amount of force..you gotta go manual now.

So, just gradually move the bolt back and forth..actually slightly up and down...until it moves slightly...then spray more WD40 on it..use the pry bar to put pressure on it..and slightly move it the direction you want the bolt to move. Be patient...yes, this may take a while to do. We spent 45 minutes on one upper control arm bolt once...and this was with three knowledgeable people working on the issue at the same time. THAT bolt was bent, stripped, and hammered in by a disreputable shop prior to us ever working on the car. We had to fix their mistakes.

Be prepared to fix the threads on the bolt once you have it out...or preferrably just use a new bolt when reassembling.

SFG Performance
Fremont, CA