Knocking / rattling from rear of W126
 

My sons 1989 300SE has a loud rattling / knocking type noise from what sound like the left rear of the vehicle. It knocks and rattles like mad driving around town. It completely disappears on the highway. I can't find anything loose in the trunk. I can not hear the sam noise if I push down on the rear of the vehicle. Any ideas?

Sounds like the CV joints on the rear axles.

Check the sway bar link. The ball joints go bad and make a loud knocking sound

w124 - same rearend noises
 

Is replacing this sway bar link a simple unbolt, install procedure? I have a parts car and easily could see if this swap does the trick. Thanks

Yessir, it sure is. With the wheel off, shouldn't take 1/2 hour...

Yep thats what I was thinking.

Check the sway bar to body bushings as well -- a missing bushing will make horrible noises.

So will missing rubber at the top shock mount, or a loose bottom bolt on the shock.

Peter

Wheels coming off tomorrow and I will check all the above. Thanks for the input. I'll let you know what I find.

I have the same rattling sound in my 300SEL...it's not very loud, but I can hear it when I have the stereo off, driving around town and it gets a bit annoying. It honestly sounds like a slightly loose shockmount to me... are the upper shockmounts located inside in the car or am I way off? I can't seem to find them...but then again I haven't looked underneath the car yet...LOL

Had the same noise on my 300SD and it was the sway bar links. I would just replace them while you are there. They are not alot of $$$.

do sway bar links first before anything more expensive. they are cheap, don't use used ones. apply penetrating oil first so you don't break the bolt off like my mechanic did!!

Reviving a 5yr old thread...

I have a similar rattle coming from the left rear wheel when going over bumps. Sway bar links have been replaced and the swaynbar-body bushings are good. Exhaust hangers are fine. Upper and lower shock mounts/bushings are fine.

Wondering what else this could be...how could I check to see if the CV joint is bad? Could a bad bearing be making this rattle?

Thanks for the help, everybody!

First check the exhaust, Just move it around (when it is not hot!!) and see if it hits anything.

Mine made a strange noise when one of the mounting rubbers was bad.
It only made the noise if I moved the exhaust a lot to the side.

Rob

Noise
 

That was the source of my noise last year. I took apart the connection and used a lubricant on the bushing as a temporary fix until I get around replacing the both links. The noise has not returned yet. Easy fix and not a lot of dollars as previously stated above.

If you are coming up empty-handed, there is another po$$ibility, the caliper bearing brackets.
Hope it isn't cuz it's a huge job, here is a link that shows the job, it is a PDF so you will have to click to allow the download:
http://www.google.com/url?sa=t&rct=j&q=&esrc=s&frm=1&source=web&cd=3&ved=0CDwQFjAC&url=http%3A%2F%2Fwww.benzworld.org%2Ffo rums%2Fattachments%2Fw126-s-se-sec-sel-sd%2F291870d1266619920-rear-wheel-bearing-replacement-procedure-needed-35-360-rear-axle-caliper-carrier&ei=SFyhULiiMabUyQHA7YD4DQ&usg=AFQjCNG3_MQ5xVbI-Cyzas3Ysr4pZxsuGA

Caliper carrier MB calls it, I think parts dept called it a bracket. Anyways it's a real pita.