W108 rear end compensator
 

Looking for a hydronuematic compensator in non working but repairable condition.
Any help would be greatly appreciated.

Where are you? How are you planning to rebuild it?

Late reply
 

Scooter, sorry it took so long to reply to your questions. I am in Nashville. I ended up buying a broken hydro and turning it in for a rebuilt one from Niemoller. If anybody is thinking about going to a hydro compensator from the spring I would highly recommend it.
Brad

Sorry I missed your post. I have a functioning compensator on my SE that I am sadly getting rid of by Christmas (or else, Mama aint happy)

Why? Is it noticably better? I've only ever driving one with a spring so I have no reference for comparison.

- Peter.

The biggest difference is the advantage of having the camber correct no matter the load. The car also rides and handles well when both loaded and unloaded.
I now have experienced both and even though I had kingpin and other front end issues it just felt better. But hey, maybe I am justifying my expenditure. :o

There is a great difference in drive comfort and quality if you have hydrocompensator on rear axle.

I have on my w108 rear axle which bought 14 years ago and driving car only summer time and nothing happened. But as a disadvantage, You can't load car and trunk at the same time full like spring. As the system works on hydraulic fluid over high pressure as a damping medium(As I remember correctly around 75 bar pressurized Nitrogen filled in), in the case of falling in ditches on bad roads when car fully load, high pressure nitrogen can destroy piston oil ring and gets out from hydromat upper cap rubber manchette. Finally gets defective and car rear drops down as the pressure decrement to 0)

In the past I worked on this hydromats as a curiosity to check what exist inside) and open one which I bought from dismantler about 20 years ago. Hydrocompensator was defective and even I can push piston with my hand till almost half( normall you can't move piston even mm by hand) so losen upper cap and piston flew away and hit the concete wall and destory it. As it's written on outer chamber that never open even defective)) I repaired oil gaskets and replaced oil rings on piston and check the condition of 2 rubber chambers, filled with thich suspension fluid and pick it up back.However, the problem here is not repairing the compensator. For me, problem is how to and from where to fill pressurized Nitrogen into compensator. I guess, Boge has special filling aparatus to fill from 2 star screws which are on the outer chamber as well or its filled in already pressurized medium.

Because if you use special nozzle to fill compensator with high pressurized gas, here its over 70 bar Im sure, at the time filling is completed how you can close seal it? Because it gas will escape to air. This is the part that I still don't understand, if I find solution it's not so mcuh difficult to repair I guess, unless in rubber chamber inside are torn? Which is imposible to find anywhere. I think this is the criterion that After inspection Sachs says after inspection that Hydromat can't be repaired.

Sorry for my detailed maybe boring story just expained my experience with this weird useful device)

Regards,

Kutluhan

My hydropneumatic compensator was not working so I replaced it with a spring. I wasn't happy with the spring as the car sat high and the rear wheels had noticeable positive camber.

I sent my hydropneumatic compensator off to Mercedes Classic to have it rebuilt. Now that i have the rebuilt one in the car, the camber and the ride height are correct. The car rides better and handles better on corners with the slightly negative camber. With the spring in place, I felt like the rear end was on tippy toes, and it was not a comfortable feeling. It was expensive to get the compensator rebuilt but worth it in my estimation.

How expensive? :-)

$1400

FYI For anyone looking into replacing your spring for a hydro compensator you need a core to turn in.

The one mentioned in my reply post, comes with a free car :D

I wanted to awaken this old thread and see how the rebuilt compensator was performing? It'd be great to have some feedback on the niemoeller rebuild.

I'm lucky enough to still have an original one in my car. It was on the W108 4.5 axle that I installed 30yrs ago, and it has survived the car being poorly stored (because I'm an idiot) for 10yrs from 2009-Jan 2019. Car still sits level with correct camber, and appears to pump itself up. My car previously had a spring, which I kept. I just purchased a used compensator on ebay so that I have a spare to get rebuilt, should that time ever come.

It's interesting with all the hacks, mods, and DYI's on the interwebs, that no one has ever figured out how to disassemble, repair, and pressurize these. They're the black magic of the automotive world!

I agree about the black magic. I believe it was a french engineer who invented the idea, I originally wanted a W114 250 from around 1970 because of the fully articulated rear suspension. I drove one in my early teens and can testify to how well they handled severe steering inputs. After driving a W111 sedan 200 I almost wrecked it when the dreaded swing axle camber trip almost got me. But I found the W108 280 SE first and the hydro self leveling intrigued me enough to accept the swing axle as I don't drive as severely as I used to in my youth.
I would be tempted to get another one to put on the shelf just in case. My rebuild unit from Niemuller is still working after three years. But then it seems they fail more often from lack of use.
My only problem is the combination of new springs with the narrowest rubber caps and rebuilt compensator with fewest install shims still resulted in the car being a tiny bit too high in the rear. But to the eye it seems to have settled, but I haven't measured it.
Any yes it drives like a dream. It's such a contrast to modern cars that don't seem to handle potholes, speed bumps and uneven surfaces as well.
Brad

Hi Brad. Thanks for the input, and I'm glad yours is still working. I didn't drive mine long enough with a spring, and that was 30yrs ago (because apparently I got old) when I was 28, so I don't really remember. I was also changing the height of the car, because for whatever reason, it was very high all the way around. But I will say; with the compensator, it has a very dead/stable ride.

During the purchase of the compensator on ebay a couple weeks ago, I called the local dealer to purchase a new rubber boot, and the wire "clamp" that secures the base of the boot. I asked about availability. Compensators are still NLA. The boot is NLA. The wire clamp was available from Germany. I ordered a new boot from niemoeller and it arrived the same day the used compensator arrived.