Informative post. I have been chasing a rear thump in my 94 wagon as well. I replaced the accumulators, rear sway bar end links and the upper ram bushings, I had some improvement but the annoying thump is still there. More so on the right side then the left. I sort of gave up figuring it will get more obvious with time and then I'll spot it. I have had it up on the lift any number of times but cannot see any obviuos bushing problems. I know at this point it's probably the sub frame mounts.

With respect to the last comment about adjusting the ride height mid way between the high and low point, does this not result in the rams carrying some of the load? It would seem that anything less than the lowest setting is allowing the rams to carry weight. What am I not getting?

Thanks,

John

__________________

My 240D Gallery http://www.peachparts.com/shopforum/vbpicgallery.php?do=view&g=290

Sorry...forgot an item or two.
Let me clarify....I forgot to say I hang on the rear tow ball or cargo door to pull the vehicle down as far as I can....this does two things...compresses the rams and allows the springs to carry the weight.....if you measure or remember where the car sits lowest and highest ...split the two and you'll be very near to spring height.

Failing that ...the idea is to allow the rams to act as shocks ....not load levelers when empty.

The idea is to get the springs to carry the car rather than the rams, as they will be under pressure if set too high......and the top ram mount will be already compressed and a road bump will translate into a THUMP.

This is not an exact science and some of the cars I work on carry a constant load in the rear which causes the factory setting to be harsh.

The one here now has a Mobility scooter and a scooter electric lift in the rear. She was complaining of very harsh ride with noise.

I shall have to fit spacers to the spring seats to level out the wagon, as the added weight has caused the rams to be carrying most of the increase....making for all the noise.

Sorry about the confusion....I knew what I was talking about...it just didn't come over properly.

P.S. It is acceptable to allow the rams to carry a little weight if your rear springs have settled slightly....and lifting the rear about 3/8th or so seems to have no affect on ride quality, but lifting it higher or trying to level it out because there is serious spring sag or a constant extra load in the rear will make it noisy.

P.P.S.......If your accumalators have more than 6 years on them the nitrogen will have nearly all gone. the suspension will thump if this is the case.

The roll of the spheres is to act as a cushion to the movement of the rams and if the rams are too high, the nitrogen will be already compressed too much and not allow for futher movement and in the case of a dead sphere it will be much worse....in other words, the rams become practically solid if the spheres are dead.( IE: All the nitrogen has leaked away....the rubber diaphram is quite thick, but will not absorb the ram shock loading.)

.

__________________
[http://languageandgrammar.com/2008/01/14/youve-got-problems-not-issues/ ]

"A liberal is someone who feels they owe a great debt to their fellow man, which debt he proposes to pay off with your money."

dk

In other threads the "correct height" appears to be an unknown. Somewhere I read the rear should be 1/2" lower than front in unloaded engine off state. Someone made reference to measuring from star center [of wheel] to fender lip to obtain a "reasonable" measure for DIYers.

Assuming all components are in good condition, should the self-leveling system maintain a near original spec?

What would be an acceptable range [+/-] measure for
1] star center to fender lip front & back wheels?
2] variance between left and right sides?

Bob

With the engine off the rams 'should' sink to spring level...but this ain't always so, as the leak down of each vehicle is different.


I find most wagons sit with three fingers clearence from the top of the tyre to the lip of the wheel arch...which with my fingers is about 1and 3/4 inches....your's may not, and indeed sedans sit lower, especially if they are not 4Matic.
The older the springs are, the more they will sag, and most shops will set the rams to compensate for sag which makes them noisy.

There should be no difference left to right with car empty...if there is, you need to check spring height and for any suspension or collision damage.

.

__________________
[http://languageandgrammar.com/2008/01/14/youve-got-problems-not-issues/ ]

"A liberal is someone who feels they owe a great debt to their fellow man, which debt he proposes to pay off with your money."

Mine are 3-1/8" top of tire to fender lip. This distance has always made me believe the rams [shocks/struts] are carrying too much of the rear load. In addition, it thumps over bumps enough to make the rear mounted CD player skip and the change in rear height is minimal after loading the cargo area and starting the motor.

Why do you "slacken off the roll bar clamps so the rod /clamp assembly is loose." rather than only disconnecting the level controller arm?

Bob

The roll bar clamps are the mount for the arm to the valve...it is easier to rotate the anchor around the roll bar than trying to adjust the slotted arm on the valve.

Your vehicle is too high if there is 3 inches of free air between the tyre and arch.

For adjustment of the spring ride height there are three rubber mounts available from MB....as well as new springs.
Rubber mounts are 8mm 13mm and 18mm in thickness....each is identified by a small nubs indicating the thickness in that order.

There is a 4mm hole in the valve and arm to line up, that is the zero point.
With the arm assembled the 4mm rod/drill should slide into the hole in the valve body after going through the arm...at this point the ride height should be close to factory....if not, it needs adjusting.

MB suggests a maximum of 9mm difference from side to side.

I suggest you disconnect the control arm and set the valve to zero and allow the height to stabilize....drive around with it still disconnected and listen for noise/thump, if it now rides quietly you can adjust the ride height if too low by adding shims or buying thicker spring mount rubbers.

__________________
[http://languageandgrammar.com/2008/01/14/youve-got-problems-not-issues/ ]

"A liberal is someone who feels they owe a great debt to their fellow man, which debt he proposes to pay off with your money."

BTW...Changing the thickness of the spring mount by 5mm changes ride height by 9mm....approx' 3/8th inch.

__________________
[http://languageandgrammar.com/2008/01/14/youve-got-problems-not-issues/ ]

"A liberal is someone who feels they owe a great debt to their fellow man, which debt he proposes to pay off with your money."

You are sneaking up on the age where you need new thrust and torque links in the rear end. The rubber goes bad, allowing the rear end to sag some, and they thump under the rear seat badly, as that is end that moves.

You will also have some torque steer when these are bad -- rear end will want to move sideways one way under acceleration and the other on trailing throttle or braking.

Much cheaper than struts.

Peter

__________________
1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!

well, I replaced the rubber shock mounts and sadly that wasn't the cause of the clunk. but whats interesting is if I leave the shock disconnected, and have the wheel mounted I'm about to bounce the rear suspension with my hand and I THINK I'm generating the noise. I say "think" because I'm not sure if the noise I do hear is the normal sound of the various parts moving or if its the culprit. now I need I second pair of hands to bounce the rear suspension wile I watch/listen from underneath. theres what, 4 different arms it could be...sigh.

Try checking out your sway bar links. When they go bad they usually manifest themselves as a clunking going over bumps. This happened on my 123 wagon. It's easy to check them. They are part of the rear suspension. An S shaped link I belive yours are metal. There have a pivot point on either end. If you unbolt one and pull it out, then you can move the pivot points by hand if they are wobbley or easily moved they are bad. If they are stiff then they are good.

__________________