Rear end , harsh thump / bang noise..

[fastcar]

I own a 1992 500E, 177000km,, had it for two years ,only drive it in the summer months when I am home,, so that's about 4000km a year,,
I have this very annoying thump or bang noise from the rear end when i drive over cracks in the road,, roads are not the best where I live,, lots of cracks in the pavement,,
Anyway,, I have checked the trunk,, space tire,, exhaust system,, suspension bushings,, and just replaced the accumulators as per what I have read on this site,, but the thump is still there, I even rode in the trunk to see if I could pin point where it ( the thump) is coming from.
It appears to be coming from around the outside end of the rearend aorund the Hyd shock absorber,
Have changed the rims and tire from originals to 17" Evo six spoke with Goodyear Z1 allseason low profile tire,, which may be part of the problem????
Does any one have information on this problem or has it happened to any of you and what are your suggestions to fix it...( install a big loud stereo unit in the car)) Ya it's coming...
Need help with this..

Thanks,
Bob

 

[arno]

rear shock absorber most likely.

a'

 

[fastcar]

Was hoping it would be something easier and less expensive,, rear Hyd shocks are about $750 each,,
anyone else have any ideas ????

 

[Taxi Driver]

Was hoping it would be something easier and less expensive,, rear Hyd shocks are about $750 each,,
anyone else have any ideas ????

Hi, have you confirmed any leak/leaks at any of the shock absorbers ? if not do look a bit
further up the trea, I mean the hydro-pneumatic cylinders mounted in the trunk, get new spheres
and you'll have a new car. I assume you also feel a little bumpy-harsh ride.? Roger

 

[arno]

rear Hyd shocks are about $750 each,

that sounds really high. i replaced my rears a few years
back and they cost $430 each.

a'

 

[gerryvz]

I'd recommend a good shop look at this situation. Your tires and wheels shouldn't affect anything.

Have you considered changing the extremely cheap four bushings that sit on either side of the rear hydraulic struts where they attach to the car's chassis? These little buggers can have a HUGE effect on ride characteristics, believe it or not.

The other thing I'd have looked at would be the rear subframe mounts, and all rear suspension rubber (i.e. control arm bushings, etc.).

I'll bet you find (if you haven't replaced them yet) that it is the four bushings where the tops of the struts attach to the chassis.

BTW you can tell very quickly if the rear accumulators are bad. The up and down motion of the rear suspension will have a very harsh damping motion (really a non-existant motion) when you press down HARD on each corner of the rear bumper. If there is less than 1 inch of travel, and it feels very "rubbery", then you have accumulator issues and you should change them ASAP. If you have a 1-2" smooth down and up motion, then your accumulators are OK.

Struts don't fail very often, but it's often obvious when they do because they leak hydraulic fluid externally and you can see this pretty clearly. Generally the rear accumulators are the part that fails more frequently. The issue is, that if you drive the car with bad accumulators for a while, the lack of damping in the accumulators (which provide the springing capability) will cause the struts to blow their internal seals and fail, because the hydraulic fluid in the system has no place to go but out of the struts' seals.

I'd drop the subframe and inspect all of the rear bushings, and also at the same time REPLACE the four rubber bushings at the top of the rear hydraulic struts where they pass through the holes into the chassis.

Cheers,
Gerry

 

[need2speed]

Sounds familiar Replacing all the rear links and bushings cured similar noises for me...your mileage indicates you are about due anyway. Try that if you don't the problem in the rear struts.

 

[fastcar]

Thanks for the info,,
I have changed the accumulators, flushed the system and added new Hydraulic oil,, everything seems fine in that area,,
Did a visual check of the bushing ,, they all appear to be in great shape,, this car looks like it was always storaged indoors by the look of the undercarrage, all rubbers, fitting, nuts and bolts are clean and rust free.

Did not find any oil leaks around the rear end area or from the struts when the accumulators were changed..

SO,, I think the step would be as Gerry mentioned,, change the four bushings on the rear hydraulic struts...cheap and easy first..
and have a closer look at the subframe bushings.

Arno::: \ Where did you get the rear sturts??? The quote I got was from the MB dealer here in the eastern part of Canada,,$750..

Thanks for your feed back...

ON another topic,,, CENTER CONSOLE:: When I purchased the car,, the power mirror switch was and still is pushed down into the Center console and the small transmission selector switch E-S is missing,, have the parts BUT >>>> I do not know how to get in there without causing damage to the console.. The MB dealer said to pry the black plastic piece around the gear shift but I'm not sure about this..SO...
Does anyone have a step by step procedure of how to get into the center console without braking something??

Cheers

Bob

 

[gerryvz]

Yes, the black piece around the gear selector lever DOES lift up.

The issue with the four bushings is that they compress with the weight of the chassis on them over the years and lose their damping ability. That's the issue with chassis rubber such as flex discs, motor and transmission mounts, control arm and sway bar bushings, strut top bushings, etc. The rubber often LOOKS fine to the visual inspection, but structurally it is in poor shape (cracks, compression, etc.) due to the elements, but mostly to AGE. A rule of thumb is that chassis rubber should be replaced every 10 years.

I just replaced all of the front chassis rubber & ball joints on my wife's 1995 E320 wagon. This included full lower control arms & ball joints (these are exclusive to the wagons and the ball joints cannot be pressed out and replaced like they can with the sedans), transmission and motor mounts, sway bar bushings, front flex disk, and various other things. The difference in the ride of the car now is like night and day, and there was NOTHING obviously wrong before (the car has 165K miles on it).

It's one of the things I'm always harping on people to do - CHANGE YOUR CHASSIS RUBBER !!

Cheers,
Gerry

 

[IslandMon]

I had the same problem as you. I replaced the spheres and upper bushings and the noise still persists. I pulled out the shock on the side that the noise was coming from and noticed that the bushing on the bottom of the shock was shot. Therefore the shock had some vertical play. What happened was the sphere failed and then the bushing on the bottom of the shock took all of the stress from potholes/bumps.

Apparently the bushings are not sold as a part and the only way to fix the problem is to get a new bushing pressed in, or to buy a new shock. I am currently trying to find a similar bushing and a shop that would be able to press it in without ruining the aluminum shock.

Hopefully that fixes the problem. I'll keep you posted if I find a suitable bushing.

 

[arno]

Arno::: \ Where did you get the rear sturts??? The quote I got was from the MB dealer here in the eastern part of Canada,,$750..

Bob

i ordered them from: Rusty@buymbparts.com


hth,

a'

 

[T-500]

I'd recommend a good shop look at this situation. Your tires and wheels shouldn't affect anything.

Have you considered changing the extremely cheap four bushings that sit on either side of the rear hydraulic struts where they attach to the car's chassis? These little buggers can have a HUGE effect on ride characteristics, believe it or not.

The other thing I'd have looked at would be the rear subframe mounts, and all rear suspension rubber (i.e. control arm bushings, etc.).

I'll bet you find (if you haven't replaced them yet) that it is the four bushings where the tops of the struts attach to the chassis.

BTW you can tell very quickly if the rear accumulators are bad. The up and down motion of the rear suspension will have a very harsh damping motion (really a non-existant motion) when you press down HARD on each corner of the rear bumper. If there is less than 1 inch of travel, and it feels very "rubbery", then you have accumulator issues and you should change them ASAP. If you have a 1-2" smooth down and up motion, then your accumulators are OK.

Struts don't fail very often, but it's often obvious when they do because they leak hydraulic fluid externally and you can see this pretty clearly. Generally the rear accumulators are the part that fails more frequently. The issue is, that if you drive the car with bad accumulators for a while, the lack of damping in the accumulators (which provide the springing capability) will cause the struts to blow their internal seals and fail, because the hydraulic fluid in the system has no place to go but out of the struts' seals.

I'd drop the subframe and inspect all of the rear bushings, and also at the same time REPLACE the four rubber bushings at the top of the rear hydraulic struts where they pass through the holes into the chassis.

Cheers,
Gerry

Gerry;
My car is giving me this problem also, right side-105K km.

I remember this post, but I thought someone (yourself?) posted a diagram of the four bushings and their attachment to the shocks and chassis.

Please let me know if i'm losing my mind.
Do you have part #'s too, by any chance?

If anyone can help, it would be appreciated.

Thanks

 

[gsxr]

Rear SLS shock mounting kit is p/n 124-320-03-56, one per shock, two required per car. About $25 each.

 

[T-500]

Many thanks, Dave.
I hope this works.

 

[gsxr]

I have the same problem on my '94. I just bought the bushing kit, but I'm nearly certain it's the SLS shocks themselves. Since the new shocks do not come with the bushings, I figure I'll still need the kit anyway, so it wasn't wasted money. Oddly, my '92 is nice & quiet, despite having many more miles, and both appear to have stock / original SLS shocks. Go figure!

 

[T-500]

Hmmm, interested to hear what happens. I can't do this rightaway.

Trying to get my car into the paintshop this week, to fit my bumper and headlights. I also bought the mesh intakes from David Hendy. Rough, but will look great when painted.