Help - I can't find the source of the clunk
 

I just rebuilt the entire front end of my 1986 300SDL.

-idler arm
-upper control arm bushings and ball joints
-sway bar bushings
-lower control arm bushings and ball joints
-eccentric bolts
-guide rod mounts and bushings
-suspension bracket bushings
-tie rods
-center link
-steering damper

After I finished I still heard a clunk when accelerating or braking and sometimes over bumps while turning.

I took it to a reputable indie mechanic to align the front end and check over my work and try to find where the problem is.

They said the passenger side upper control arm bushing was defective and they replaced it. They said the clunk was gone and I could pick up the car, but when I drove it home it was still clunking.

I decided to take it to another mechanic I use for inspections. They thoroughly inspected the front end and couldn't find the clunk either. They said they couldn't hear or feel it to begin with, but nothing looks unsafe.

I just picked up the car and it's still clunking.

What do I look at next? There's nothing left that I'm aware of to replace under the front end.

I had sort of the same issue with my W123.

I too rebuilt the entire front end trying to solve the clunk, it didn't cure it, hahah but it needed replacement anyways.

Turns out it was a stripped motor mount bolt which was popping up and down in the engine support arm. I guess someone replaced the motor mounts years ago and cross threaded that 8mm allen bolt and for some reason it popped loose.

Yup. That's what it was. Thanks for the info Mercy.:cool:

The driver side 8mm motor mount bolt is cross threaded and only screwed in about half way. The head of that bolt is stripped too.

Luckily I have an extra mount arm so I can drill out the bolt head, remove the mount and arm and replace it with the new arm and a new 8mm bolt.

The motor mount itself still looks new so I'll just continue using it.