Noise coming from the rear...need help disecting

[Gonzo318is]

I have '91 318is and everytime I go over a speed bump or come into a drive way I hear a "thud" from the rear kinda like the car is bottoming out. The shocks are 1.5-2 years new so I wouldn't think they're the culprit. What could this be? I want an idea before I take it to the mechanic.

[Jon325i]

Check everything back there. I experienced a similar problem on an '89 325i. Turns out one of the muffler hangers gave out and this allowed the "can" to swing about when going over bumps.

If the muffler is intact, check your rear shock mounts. You mentioned you got new shocks within the last couple years. Did you re-use your existing rear shock mounts or get new ones? If these are the problem, then fixing it isn't too bad. It would also be a good time to think about upgrading to more robust factory pieces such as E46 M3 rear shock mounts. They bolt right in. Maybe even consider getting Z3 reinforcement plates too. Also a simple bolt-on affair.

Jon

[///M42 sport]

rear shock mounts. I tried the e46 mounts but ended up popping those suckers right away. Be sure you have the proper washers in place.

[Gonzo318is]

Check everything back there. I experienced a similar problem on an '89 325i. Turns out one of the muffler hangers gave out and this allowed the "can" to swing about when going over bumps.

If the muffler is intact, check your rear shock mounts. You mentioned you got new shocks within the last couple years. Did you re-use your existing rear shock mounts or get new ones? If these are the problem, then fixing it isn't too bad. It would also be a good time to think about upgrading to more robust factory pieces such as E46 M3 rear shock mounts. They bolt right in. Maybe even consider getting Z3 reinforcement plates too. Also a simple bolt-on affair.

Jon

Not sure if the shock mounts were replaced cause I just bought the car but I do have a stack of receipts from the prev. owner so I'll ck them.

[bmwannabe]

could it be subframe bushings?

[Gonzo318is]

I'm taking the car tomorrow to a mechanic to see if they can verify that it is the Strut/Shock mount. I saw a couple of suggestions to use the E46 strut/shock mount instead. What are the advantages of using the E46 M3 strut mount and what else do I need to install this part? While I'm doing this what else should I replace or upgrade?

[Avus_325is]

I saw BMP has some nice looking rear mounts that are actually bevelled inside so that the metal tube doesn't blow out.

[BahnE30]

most likly the RSM's if there still in good shape just tighten down if the all crumbly and old buy the E46's

[///M Powered]

Taking it to the mechanic to see if it's the shock mounts?

Jack your car up in the rear,and look in your fender well, see if your shock mount seperates where it meets the well. If it's seperated you have blown mounts for sure.

[Gonzo318is]

The problem is a broken sway bar mount.

[PanamaE30]

That blows.

IE sells some sway bar mount reinforcements.. don't know if it's too late to use them though.

[Gonzo318is]

That blows.

IE sells some sway bar mount reinforcements.. don't know if it's too late to use them though.

Yeah, it does... do you have a web link for IE?