what are the signs of worn rear shocks / airsuspension?

[werminghausen]

I was driving on the highway since a long time and I noticed a very 'jumpy' ride with my 300SEL 3.5...very uncomfortable to be honest.
I though it must come from the rear suspension as I have new shocks in the front.
What are the signs for worn shocks combined with airsuspension?
Martin

[WANT '71 280SEL]

Mine feels like that if I have the knob pulled out, thus greater pressure in the back. There's no chance your pressure is turned up, is there? Otherwise it sounds like bad rear shocks. Shocks aren't too bad for these cars.

Best Regards,

David

[werminghausen]

I tested the suspension while putting body weight at the rear both sides.
The left side is not really going down when forcing weight to the suspension...while the right side goes down more smoothly.
What can this be? It seems that left side has some more resistance?
I don't understand.
I had changed the left side airbag and disconnected the airline between both airbags. But why should this change anything?
riding height is good and car is going up when I pull the knob and going down when I press the knob...so all seems to be fine.
This car is sometimes a riddle.
Compared with my W126 the 109 is jumping around on the highway..doesn't sound right...does it?
Not sure if new shocks will do the job but worth a try?

[Pooka]

I am not sure I am following you here, but it sounds like you have a leak in your right side rear airbag.

Let the car sit with the engine off. Have a friend supply air to the air tank under the front left fender and see if you can hear air leaking out of the bag.

You can also take a length of plastic tubing and use it to listen through. Put one end up to your ear and use the other end like a probe to narrow down where a hissing noise of escaping air is coming from.

[werminghausen]

Hi Pooka,
no airleaks anywhere! For some reason my car is bouncy and is not fun to drive on the highway. A Mercedes should cruise very quietly with high speeds..... not happening and this is my problem.
I don't know what makes the car bouncy.
I thought I 'd need new rear shocks...as the front ones are new- front is quiet.

[WANT '71 280SEL]

If the left rear is not going down when applying weight, like the right, the pressure must be higher in that bag. Given how the system works, I'm not sure how one of the rear bags could have more pressure than the other. After all the airbag is the only thing that really "pushes" the car up, so it must be pushing harder on that side.

Mine definitely isn't bouncy on the highway, firm and tight, but that's also because I have the tire pressure cranked way up because of the car's weight (almost 40 psi).

Best Regards,

David

[werminghausen]

David, the air pressure MUST be the same as the riding height left and right are the same. With different pressure the height changes (My car is going up when I pull the knob, going down when I push it)
The airpressure might be a thing but still I am very suspect that someting else is not in order.

I had removed the lower piston of the airbag...is there a chance that piston is not engaging properly relative to the airbag. I can't believe that something is wrong here.

I'll inflate the tires some more and see of there is less bounciness.

[WANT '71 280SEL]

Martin, I'm not suggesting adding air pressure to your tires. That makes for a harder ride, but that certainly won't cure the bounciness.

You raise a good point regarding the air bag piston. Did this develop after replacing the air bags? Or is this something you noticed because you haven't driven the car in awhile? It's always something on these cars; however, I'd still take it over a w108 and day and I say that knowing mine needs almost $2k in suspension work.

-David

[werminghausen]

Took the wheel off (again), all fine with the airbag. I popped the lower end of the shock/strut so the lower end was free- easy to do.
I can move the strut up and down by hand, same minor resistance both directions but no problem by hand.
How should it feel if shock is in decent shape?
Can you move the piston easily by hand??

[WANT '71 280SEL]

If the shock is in good shape, it should be pretty hard to compress by hand. Then the shock should smoothly extend on its own.

David

[werminghausen]

Originally Posted by WANT '71 280SEL

If the shock is in good shape, it should be pretty hard to compress by hand. Then the shock should smoothly extend on its own.

David

I ordered new shocks from the US, Bilsteins.
The old ones are shot I think.

Also I ordered a new fan clutch.. (shipping $130 grrrr)
Martin