knock in rear quarter

meo 325is · 06-08-2005, 03:33 PM

Hi guys and girls. My 1992 325is has developed a knock in the right rear. It's sounds like the shock top mount is busted but it is new and so is the shock absorber. Any ideas?? thanks

New93325 · 06-08-2005, 04:39 PM

The sheet metal around the top shock mounting hole can fracture(mine did). My 93 325i made a deep clunking noise over bumps before we welded it and replaced the rear shocks. Left and right sides were cracked.I scraped down to bare metal before mig welding it, then sprayed the repair inside and out with undercoating.It's been quiet since then. Tim

meo 325is · 06-09-2005, 03:35 AM

Thanks Tim, but is this very obvious because I just replaced both shock top mounts and I didn't see any damage in this area? Thanks again. Mark

blkongry · 06-09-2005, 07:22 AM

Can you force the knock... have a friend rock the car up and down to produce the knock and trace it? If it's not something obvious like a shock tower top, then you're either going to have to pull the wheel off and look for interference and wear marks or get the car dynamic enough to product the knock and track it down. Gremlins like these suck. I have a loose rattle in my driver's rear of my cabrio... something that showed up when I got lightly rear ended over a year ago (or should I say my girlfriend at the time got it rear ended

...it's like a tin can top rattling around in the rear and I can't find it for the life of me... everything looks good and solid on the car... nothing loose, and I can't get it to rattle sitting still.

Jeron · Jeron's Garage

Since you recently worked on the RSM's I assume you're certain that the problem isn't something loose in the trunk area. (Battery, Jack, Spare etc...)

Make sure you tightened everything properly when you replaced the RSM's. Specifically, the top bolt on the shock rod requires you to hold the rod by some means (depending on the manufacturer) and then tighten to a fairly high torque spec.

meo 325is · 06-12-2005, 08:57 AM

Hi guys, I even removed both rear shocks and the noise is still coming from the right rear quarter. The noise comes when you hit a good bump on the road!!!

New93325 · 06-12-2005, 01:18 PM

On closer examination I found the much smaller crack on the right shock tower. The left tower's cracks were easy to see, but the right side one I almost missed. You might have to remove the trunk lining material to see a crack - I did. Tim

scintaar · 06-13-2005, 04:09 AM

Have a look at your diff carriage mounts...
Underneath the car, looking straight up at the body, you should see a large rubber mount with a bolt going thru the centre.... there's one on either side of the diff carriage.
check that the centre bolt is done up tightly enough and that the mount isn't cracked or split.
I had a similar problem on my E30... turned out all I had to do was tighten them both up.
Hope this helps as my descreption might be a little vague... have a look in a haynes or bentley manual... they should show you exactly where they are.

meo 325is · 06-13-2005, 11:03 AM

Thank you very much scintaar, I will check that out and your description is pretty good!!! thanks again

kocio67 · 06-13-2005, 12:36 PM

Check http://www.turnermotorsport.com/html/detail.asp?PRODUCT_ID=4111225649

Hopefully this is not your case ( hard and costly to fix it).

meo 325is · 06-13-2005, 12:55 PM

What do you mean kocio67 by hard and costly

kocio67 · 06-13-2005, 01:05 PM

you have to remove entire rear axle plus gas tank and weld reinforcements into body.

meo 325is · 06-14-2005, 11:57 AM

WOW, can't you just replace those mounts?

Jeron · Jeron's Garage

You can replace the mounts. The reinforcement kit is to prevent and repair a cracked rear subframe. The question is; is your noise due to a cracked rear subframe?

meo 325is · 06-14-2005, 01:03 PM

Like I said earlier, I remoed bott shocks and the noise is still coming from the rear quarter when I drive over a good bump on the road. Is it easy to see if the subframe is cracked?

Jeron · Jeron's Garage

There is a pic of a crack on the Turner website listed above. I've seen other pics on the web. In the early stages, I'll bet the cracks are difficult to see.

blkongry · 06-14-2005, 01:34 PM

A notable clunk wouldn't come from an early stage crack would it? To get a sound, you'd have to get some decent movement, which means a significant crack. Also, unless you have been tracking your car hard with grippy tires, it's not really likely your mounts are tearing away from the frame. I know this is a concern to a certain degree in these cars, but usually not from a daily driver.

If you are hearing a clunk when you go over bumps, more than likely it is a loose or worn part... probably like Scintaar said. Now you said you pulled off the shock and it still does it? Then it's somewhere in the linkage or in the spring. With it being a clunk, I'd go for spring perches and movement there. Hmm, I can remember, but isn't there a rubber mount on the top and bottom of the coil springs? Are those cracked and the spring is rubbing on the perch as it's compressed/released?

meo 325is · 06-15-2005, 11:56 AM

I looked at the r/h spring the other day and it looked fine. The weather as been the s.... here lately so I havent had a chance to looked at the stuff the scintaar had mentionned.

thank you very much guys for the time and help. Meo