I have recently bought an '88 420SEL for my daughter; while it had only 75,000 miles and had not been driven much in the last few years (a grandparents' car), it did have a creaking sound in the front when going slowly over bumps. I have had the various joints lubricated and replaced all four shocks with OEM Bilsteins. The creaking is much lessened, but now I am getting a mild bumping sound ("budubba, budubba")when applying the brakes on a coasting stop, going slowly over speed bumps and on low speed turning. The noise does not appear on harder braking. Any suggestions would be appreciated - is the caster support rod joint the culprit?

I can sympathise with you. I bought an 85 with 81,000 miles on it and too many years of Texas heat. All of the rubber on the suspension parts is/was cracking. I still have the creaking front end. I imagine it is partly due to the spring pads. I also had to replace the "brake force guide rod bushings" or "caster control rod bushings" or 10 other terms for those dang big ole bushings. I can tell you this...with the springs in, it was a PAIN to get the parts lined up again to get it all back together.

I also had a clunking noise coming from the center support bearing of the drive shaft. You could feel this one with your hand over the hump in the rear floor board.

Good luck! I still have to replace the rear subframe bushings and differential support, as well as the upper control arms in front.

I had a 84 500SEL that used to make a thumping noise in the front end also. Connected to the lower control arm there is a rod that runs toward to the back of the car...not sure what it's called but where it mounts to the body there is a rubber mounted ball and socket.

Replace these and noise will be gone. Trust me I spent way to much time trying to find that solution!

Tox!

It call guide rod mount kit #126-330-13-35 you need two kit to do this job also replace lower ball joints.

My 300SE W126 with 115K miles had this irritating sound - except I don't hear it while braking. The noise was most apparent when going through a speed hump.

Did all that was suggested here, in particular - replaced bushings, and the noise has gone down by 95%. There is a remainder 5% - pyschological [b/f].