rear suspension bouncing in the 300TD - PeachParts Mercedes-Benz Forum

JDmills · #1 01-07-2005, 04:15 PM

If am really frustrated! just replaced both Accumulators in november, as well as putting new shocks on the rear (used).

Going down the road today, and the dang thing starts bouncing like the shock's are worn out. I remember reading that bouncy/harsh ride charactoristics are usually the accumulaters, and the shocks are fine unless they are leaking. Is that correct?

If so I hope the accumulaters are under warranty!!
Thanks
Jason

michael cole · #2 01-07-2005, 04:28 PM

could be air in the system.there is a bleed proceedure.do a search here

RichMason · #3 01-07-2005, 04:35 PM

see if it is adjusted too high.

R Leo · #4 01-07-2005, 04:37 PM

The TD's hydropneumatic suspension is self-bleeding. Make sure you have the correct amount of fluid in the reservoir and, confirm that the link from the sway bar to the positioning valve is still connected.

#5 01-07-2005, 07:48 PM

if you replace the air cells and there is no leaks anywhere,bleeding or adjusting or a broken linkage is it-- Dennis

JDmills · #6 01-07-2005, 09:54 PM

YAHOO, I would much rather fine tune and bleed the system than replace the accumulators again. will follow the posted advice on a mission tomorow, to get my car riding like it should, rather than the horse and buggy version that it has today.
Thanks to all for your imput.
Jason

BIGRED · #7 01-08-2005, 12:03 AM

I just repaired my TD rear suspension. In my case the accumulator replacement not only cured the need for Dramamine, but it rides so so smooth.

Have you checked to see if the suspension will rise and lower as it should by manually manipulating the control valve?

Don

JDmills · #8 01-08-2005, 08:31 AM

Don,

The thought of checking the height control valve has not crossed my mind, I will check that if I runout of options. Not sure how that can effect the bounce that I get when the car is just parked. (using my foot to bounce the car, the drivers side seems to have uncontrolled rebound, where as the passinger side is not quite as bad...)
Thanks,
Jason

JimmyL · #9 01-08-2005, 11:02 AM

From what I can tell on mine, the adjustment linkage just affects ride height, but not the "bounceness". I guess if it was at a low sag, it would have more room to bounce higher, than rebound to the much lower position. The more I type, the more I talk myself out of my original point.

A lower adjusted system would I believe have less fluid to the accumulators, resulting in more bounce?
I do know that the linkage itself has inner bushings on both ends that crumble away to nothing, and that adds slop to the linkage, affecting the adjustment.
Man, alot of help I was.....

JL

R Leo · #10 01-08-2005, 11:27 AM

Quote:

Originally Posted by JDmills

YAHOO, I would much rather fine tune and bleed the system than replace the accumulators again. will follow the posted advice on a mission tomorow, to get my car riding like it should, rather than the horse and buggy version that it has today.
Thanks to all for your imput.
Jason

Repeat after me: "The TD's hydropneumatic suspension is self-bleeding."

BIGRED · #11 01-08-2005, 01:54 PM

I made the suggestion to test the control to confirm that the pump was doing its part. I assume if the fluid does not go through the system as it should, it could cause issues with the accumulators. From a technical standpoint the pump moves the fluid through the system, the control valve determines if the shocks need fluid or need to loose it and the accumulators provide the dampening. I find it hard to imagine that new accumulators would fail, but anything is possible.

Don

phidauex · #12 01-08-2005, 01:58 PM

If you look into the fluid tank through the dipstick hole while the engine is running you should see disturbance of the fluid from the pump return.

The system is self bleeding, but you can help it out by manually raising and lowering the linkage. My passenger side strut 'clunks' on bumps, even though the ride is comfortable and self leveling works fine. If I disconnect the linkage and manually raise and lower the rear-end, the clunking gets much better. I suspect that a tiny bit of air is getting into the system that mostly bleeds itself out, but can use a little help.

peace,
sam

JDmills · #13 01-08-2005, 05:50 PM

R Leo, Got it!

Seems as if the drivers side is sagging, passinger side is ok, also low on fluid, expect to find a leak on the drivers side somewhere. Be it the shock, or hose to the shock... Oh well, it is only money.

Jason

R Leo · #14 01-08-2005, 06:49 PM

Operating at 130 bar to 185 bar, if you have a leak in that system, you'll immediately have hydraulic fluid dripping off the car, somwhere close to the leaking part. FWIW, right now my other wagon, Passion Flower, is dripping from the left strut...it's been that way for 20k miles.

A bouncy (not harsh bouncy) ride is indicative of no fluid in the system or struts that are shot...however, I suspect that you'd have a leaking strut long before the damping was completely gone. A harsh bouncy ride is a bad accumulator(s).

Here's more.

dieseldiehard · #15 01-09-2005, 02:45 AM

Another cause for extreme bounce is if the linkage arm that drives the levelling valve gets loose and drives the shocks to maximum height you will bounce like crazy. BTDT - it will scare the living bejeezuz out of you if it happens, the bounce is very severe!

Also a warning to anyone messing with that valve, you must never be under the car if you plan on staying alive or at least losing your breath if the car comes down suddenly when you move the valve to remove pressure from the shocks, engine not running or running for that matter. If the car is level at idle the valve is probably set correctly.
If its high the car will look raked, and that is enuff to increase the bounce. If it is adjusted (or stuck) all the way up the car will look like a snowplow. Well, I haven't seen a snow plow in 15 years but you know what I mean.
I doubt JDmills has bad accumulators, if its really bouncy on one side and not the other it could be a shock I suppose but I thought they only fail when they leak. I had one blow a seal in 15 degree weather on a trip once, not a nice feeling to see a big puddle of hydro oil on the pavement after I started up. Luckily it wasn't a complete failure and I had a jug of fluid with me so I could limp home (some 1500 miles). I had the rear $hock$ replaced after I got back.
DDH