Rear Suspension Knock

[brock]

Hey Everyone!

I took some time to inspect the rear suspension of my car for worn parts. I have a prominent knock that's heard when going over bumps. All the suspension links look to be in good shape and I couldn't locate excessive movement. My SLS struts are not leaking. The accumulators were replaced within the past year. I don't know when the SLS fluid and filter were changed last.

When I have rear passengers, the knocking goes away.

What should I look at next?

 

[nocfn]

Brock, the bushings that are on either side of the upper attachment cushion the frame. If original, they can loose their rubber properties and are hard with no cushion. If it is not that, then the weight is causing the the struts to adjust and it goes away. Check the bushes up top, cheap fix. May want to
Manually raise and lower. If that doesn't remedy things, and no issues with links or bushings elsewhere....then the spring leg may be going. Others may discuss, my banging subsided on the w126 with new bushes but was eliminated with replacement strut.

 

[samiam44]

Did you inspect the subframe bushings, and support joints first to eliminate them from the possibilities.


M

 

[gsxr]

#1 suspect: SLS shock/hydro-leg bottom joint, which is not replaceable separately. Very common cause of rear suspension "loud knock" noise. Read this thread for some photos of the offending bushing and someone's creative use of incorrect (see post #25) BMW parts to fix it.

The rear/lower wheel carrier support joints are probably shot if they are original, but those usually squeak/groan, and do not knock/clunk. Details on those are here.

 

[nocfn]

Thank you to the "others" who added!