Frt Suspension Noise

[4RINGSx3]

Have a '95.5 S6 with 139.3K miles. Car was lowered (H&R Sport springs & Bilstein B8 Sport shocks) at 73K miles (Oct. 2001). Currently experiencing a clunking noise in front suspension; this occurs when going over minor road bumps such as manhole covers that are slightly below adjacent road surface. I'm on my 3rd set of front H&R springs due to broken frt spring (parts replaced by Bilstein for free; most recent set just installed at 138.8K miles. Today had lower control arms, sway bar end bushings & inner control arm bushings replaced (along w/ a 4-wheel alignment)and noise is still evident. I'm at a loss as to what's causing this. Work is being done by a very competent shop that specializes in suspension setups (they also performed the initial lowering modification & have done my work for many years). I did notice that the most recent broken spring set had a vinyl wrap around approx. 50% of the coil, the replacements did not, would that make a difference? Any ideas where to look next...CV joints (boots are in good condition), shocks, lose steering rack or ???. Thanks & HELP!

[UrS4boy]

You didn't mention the suspension strut bearings (aka upper strut mount) or the ball bearing support being replaced. Items 32 and 36 in this diagram. They will clunk or groan if they have failed. Item 36 made by a certain German brand name but in China have been known to fail quickly and badly.

[4RINGSx3]

Thanks Dave, I was hoping you'd see my post & reply...always marvel at your insight & knowledge regarding URS4/S6. Looking back in my records I did not find that strut bearings or ball bearing supports have been replaced since I've owned the car (12/1998 w/ 46.5K miles). Talked to owner of shop that performed work I referenced in 1st post about condition of strut bearings & BB supports, he said he inspected and they were good. Is it possible these components would cause this noise only under load /weight of vehicle fully on suspension? I'd like to narrow things down on this problem as much as possible before proceeding further. Going for another test drive early next week. Again...Thanks.

[UrS4boy]

Having complete a complete front suspension overhaul last summer (with some of the bits being on the car from Oct 92), I strongly suggest that if you have a clunk and you are *SURE* it isn't another broken H&R spring, then you should seriously consider replacing Items 32 and 36 in the diagram above. Furthermore, avoid made in China stuff and buy from a dealer. TRW and Febi/Bilstein are OE parts suppliers with a good quality record. Unfortunately, to get the ball bearing support installed correctly (there are certain grooves that need to mesh with the concave suppoer), you need to remove the struts (again).

This one had been installed incorrectly by the shop I had used before I got a garage. The result was the stud ends on the concave support, instead of fitting into grooves in the ball bearing support plastic, they crushed their own grooves which caused the bearing to effectively be inoperable (it groaned badly during parking manuouvers). I used a bit of silicon sealant to stick them in place when I replaced both sides last year.



Here is the front suspension strut blown up and annotated:

[4RINGSx3]

I strongly suspect the strut bearing & BB support (AFAIK & per my service records they have never been replaced + a lot of miles). Also noting that now getting a noise similar to the clunking but certainly not a severe when turning steering wheel (most noticeable when doing maneuvers like parking). Going for another test drive w/ tech at alignment shop tomorrow night.

[Joe100S]

You should also take a VERY close look at the nuts on the sway bar. This holds the whole shooting match together and they have been known to come loose.

[4RINGSx3]

I just received a pair of ball bearing supports (4A0-412-249) and suspension strut bearing (4A0-412-377-C)...they are scheduled to be installed in a couple of weeks.

However do have a question regarding part no. for strut bearing (aka upper strut mount). The part number on the label that was stuck on the bag containing these parts is 4A0-412-377-C however the part number stamped on the metal flange of the part is 4A0-412-383-B. The part looks the same as in the photo of UrS4boy's 4/26 post below. Is this still the correct part? Thanks

[UrS4boy]

Not to worry. 4A0-412-383-B is the casting number for the metal base. 4A0-412-377-C is the assembly number (the complete part) for the base, the rubber insert and the final middle metal bushing. You're good.

Make sure whoever installs those plastic 4A0-412-249 ball bearing supports that they line up the cast indents in the plastic with the three heads of concave support stugs. Use a little silicon caulking to hold them in place until they are added to the strut assembly (and then check again before the top nut is tightened down).

[4RINGSx3]

Update...Both frt strut bearings & ball bearing supports were replaced today (@ 139,400 miles). Seemed to help a little but noise remains. Old BB supports were OK (not cracked as in photo you provided Dave) but were replaced w/ new anyway (notches properly aligned). Nuts at sway bar are tight and H&R Sport springs are OK. Bilstein B8 Sport shocks are OK too.

The only thing that we can think of that's yet to be replaced are front & rear subframe bushings. Part nos. I've found are:
Front - 4A0 399 415B
Rear (left)- 4A0 399 419E Rear (right)- 4A0 399 420E

When a small pry bar was placed at the rear bushing locations movement is detected...right side seemed to have more movement than left (right side is where the clunking noise is more prominent). Before replacing these we're thinking about driving car with audio tester/detectors (small mics temporarily mounted at these locations & listening w/ headphones) to hopefully confirm if this is origin of noise. Could weakness in these subframe bushings cause the frt subframe to bang against the chassis thus causing the clunking noise when encountering bumps? Thoughts??

[UrS4boy]

It is possible it is the subframe mounts (your numbers are correct BTW) but it is also possible that you are missing or have loose bolts. Have a look at this pdf and check the torques:

http://12v.org/urs/FrontSuspensionTorqueValues.PDF