560SEL - Knocking sound going over bumps - PeachParts Mercedes-Benz Forum

hbofinger · #1 06-20-2009, 02:22 PM

Hi,

1989 560 SEL with 120k miles, all original shocks an so on: I am getting knocking sounds out of the front suspension while going over even small bumps, especially on the right side.

A couple of notes:
(1) The feel does not transfer to steering.
(2) Had alignment done two years ago, it was near perfect, required little adjustment. Had alignment done again recently, mechanic threw me out without charge - it was perfect, no changes needed, everything tight.

(3) Had another mechanic look below when doing my regular 3,000 mile oil change. He saw nothing obviously wrong, but thought he heard the knock came from the front strut.

So is this enough to go by and start ordering some new Bilsteins, or is there something else obvious I should check first? Again, ball joints are tight supposedly, alignment is dead-on, tires are new, but old tires wore evenly.

Thanks in advance!

Oh - for those who know me from previous posts - I had disappeared for a while because of an intensive work schedule with lots of travel. But it's still the same 560SEL I have, dubbed the "Queen Mary", black on black.

Oracle12345 · #2 06-20-2009, 08:37 PM

guide rods

bsmuwk · #3 06-20-2009, 10:32 PM

I would think strut mounts are worn out causing the strut to bang up against the body and make that knock noise.

Check for cracks on the bushings/mounts.

Oracle12345 · #4 06-20-2009, 11:51 PM

Quote:

Originally Posted by bsmuwk

I would think strut mounts are worn out causing the strut to bang up against the body and make that knock noise.

Check for cracks on the bushings/mounts.

the w126 suspension is the same as the w123's. The only exception on the 560sel is the sls.

check the play of the guide rod bushing. you can eyeball your shocks by seeing if you can see any oil starting leak out of them.

frikkiej · #5 06-21-2009, 05:06 AM

Had similar problem. Took six months to find that the suspension knock was actually coming from the bonnet catch. Not the hook. The latch itself where it is fastened to the bonnet. The welding came loose. Give it a try.

brooktre · #6 06-21-2009, 06:44 AM

It was the sub frame bushing on my car. Very pronounced knocking going over small bumps.

hbofinger · #7 06-21-2009, 03:19 PM

Thanks everybody!

No leak from the shocks - 100% dry. Will check out subframe bushings. Guide rods - is that not something (play) they would check out during an alignment?

david s poole · #8 06-22-2009, 03:22 PM

no it's not. there is a rod going backwards to the body on an angle.it terminates at a joint at the body.these are somtimes called castor joints as that is where the castor adjustment is.they are usually gone in every 126 body that i see and at 500-600 parts and labor [with alignment as it is destroyed during fitment] there are not a lot of volunteers to have the job done.

tarheel75 · #9 06-22-2009, 04:01 PM

I am experiencing a similar problem with my 92 300E 114k miles. I get a rattle like noise on my left front suspension. Had it aligned at 110k by an indie MB shop and currently tires are wearing OK. Just replaced my front shocks with Bilstein Comforts. Its been suggested that I my problem maybe "control arm bushings". It $ound$ like its a $hop diagnostic trip to find the problem and have it repaired. I may not have the special tools to make it a DIY.

tarheel75