Shocks/hydraulics suspension bumping on 1987 560SEL - PeachParts Mercedes-Benz Forum

American28 · #1 11-02-2002, 06:03 PM

Thanks for any help.

On my 1987 560SEL there is bumping or bottoming out of the suspension when going over most bumps. If I am going 60mph there is hardly any noise or it is not noticeable. If I am going 35mph they are more frequent and louder and if I am going 5 to 10 mph it is a loud hit or bump. It seems like the shocks are bottoming out. It seems to be happening on the front and rear shocks but more loudly and more frequently on the back - its kind of hard to tell but thats what it seems like. So alot of times even though I am obviously going over the same bumps with the front and back suspension the noises will only sound like its coming from the back. Other times it will come from both front and back?

Any suggestions would sure be appreciated. I have worked on my own cars all my life but have only been recently working on my Benz. I'm pretty good with tools but if you can explain any work you suggest I would appreciate it.

Thanks,

Lance:

psfred · #2 11-02-2002, 09:02 PM

Lance:

Any benz with good OEM shocks shouldn't "bump" like that. I would suspect that all four shocks are going, if not gone. Do you also have porposing over dips, or excess sway on curves?

The thump cannot be the suspension bottoming out unless you have hit a really big bump -- there is an amazing amount of travel. I think that what you hear is the shock only working for part of the suspension travel -- free movement up to where it starts to work, then it thumps. Also, check the rubber mounts on the top mount -- they can go bad, and if loose, will thump.

Peter

American28 · #3 11-03-2002, 08:22 AM

Thanks very much for the info.

I will look at the shocks and mounts today. I assume that the old "push down the bumper and see if the car bounces up and down" is still a reasonable way to make a rough assumption on if the shocks are dead or not - does that seem correct?

Does it make any sense that it might have something to do with the hydraulics of the suspension system. Looking through threads on this site and talking to others I have begun to understand this system but it is still very new to me. Does this system "limit the travel" or just adjust the height of the shock for weight distribution purposes. Ultimately could it have anything to do with my problem. Either way thanks for any help! I appreciate it!

psfred · #4 11-03-2002, 08:42 AM

Oh, yes! If the hydraulic suspension is like the self-leveling suspension in the wagons, there are nitrogen filled "accumulators" that act as springs. When the nitrogen migrates from the accumulators to the oil, as it eventually will, the ride gets harder and harder until the suspension is essentially locked -- the fluid cannot compress, and there is no expansion space for it in the accumulators, either. Only the tires provided any spring, so the rear bounces like crazy.

I'm not familiar with the hydraulic suspension, though, but I'd bet you don't have shocks like a spring suspension and that the accumulators, if you have them, are shot.

Bouncing the bumper will work fine to test -- if the accumulators are full of oil, only the tires will bounce, suspension travel will be very limited.

Peter