w124 rear suspension klunk
 

Looking for the source of a clunk that sounds like it is coming form the drivers side rear seat area when I go over larger bumps. I initialy thought it was the exhaust hitting something but it doesn't appear to be the case. Shocks seem to still have damping. Muti-link bushings and subframe mounts appear to be OK but I'm no expert at what to look for. Anything that doesn't look ripped or frayed or pushed out of place should be OK right? Any suggestions on possible causes of this KLUNK or diagnosis proceedure I should follow? I'm prepared to spend the weekend under the car poking and proding but need some guidance.

Thanks

Don't know where the top of the rear shock is tied into your vehicle, but I had the same "clunk" as you describe when I owned a 1984 190E. It's top mount was accessed via the trunk. Lo and behold the top bolt was loose and the resulting play caused it to clunk. Just a thought.

Good luck.

Brian

in order:

Sway bar mounts. Sway bar link to spring link.

Shock mounts, upper first, then lower (look for frayed rubber).

Torque link from wheel carrier to inner part of subframe (inner end).

Thrust link (diagonal for and aft from bottom of wheel carrier to front of subframe), usually front bushing.

spring link.

signs of trouble are shreds of rubber around the bushing.

Bad links will cause torque steer (car steers one way on acceleration, the other way coasting) and thumps under acceleration changes. Bad swaybar bushings or links will cause thumps going over bumps with one wheel.

Peter

A commonly overlooked source of "clunk" in the rear of a 124 car is the differential mounts. Unlike earlier cars, the differential is mounted in rubber mounts.

One mount is at the front pinion part of the diff and has a bolt that goes vertically through a couple of large rubber "washers." Those will usually not give a clunk.

The other two are horizontal with bolts that go from rear toward the front at the top rear of the differential mounting the diff to the subframe. This is a somewhat common failure.

To check them, raise the car safely and look at these rubber bushing looking mounts at the rear of the diff. If they have failed, the bolt will not be in the center of the bushing and if you raise the diff slightly with a floor jack, or MAYBE by hand, you will see those bolts move in the mount.

Good luck,

In my case it was the diff mounts causing a clunk

Thanks for the advice. All the bushings looked OK but when I removed the drivers side shock to look at the bottom bushing I found the shock to be broke. Very little pressure or damping and a lot of play. The manual suggests that it is the piston inside that has failed. Odd that I couldn't tell by driving it.

The service cd says that they can be replaced individualy. Is this sensible on a car with 100k miles or should I replace all of them?

Re. the diff mount bushings. Mine checked out OK but I wonder, is it acceptable to jack the car up on the diff? If not how do you go about lifting the car?

Thanks

Are the two rear differential ones easy to replace?

Haasman

The two rear differential mounts? I really have no idea. I suppose if they are difficult to replace and I risk damaging them by jacking on the diff I should find another way to lift the car, but I'm not sure how.

To replace diff mounts you must lower the diff with the driveshaft removed, and use a driver tool to get the old ones out and new ones in. An air chisel, carefully applied to collapse the ring on the old mount usually works better than a puller, they are usually rusted in place.

You MUST note the location of the side of the mount toward the diff -- new one must be exactly the same distance out from the subframe.

Peter

Yes. deCarbon type shocks maintain their damping characteristics until end of life unlike conventional hydraulic shocks, which slowly degrade, so deCarbon type can be replaced singly. The other three could go another 50-100K miles.

Failure is usually evidenced by significant oil leakage, but this one sounds like somthing broke inside.

You will probably find that buying a Bilstein replacement is cheaper than the dealer, and it should be the same shock.

I've never had any problems jacking my 190 up by the diff, and I always use a wood block on the jack puck, but some advise against this practice.

Duke