Hydropneumatic compensation spring

[ggdtr5]

Hi there I am looking for some advice regarding my hydropneumatic compensation spring on my 280SL.
The rear end is significantly lower than it should be and the camber of the rear wheels is very negative ie splayed out. I am suspecting that the compensation spring set up is weak as new springs (front and rear ) and shockers were fitted a couple of years ago.
I got it up on the ramp today for a look and the only obvious thing is that the right hand side ball pin seat seems to be breaking up.
I have checked a couple of suppliers websites and cannot find any spares or part numbers for this set up.
My questions are:-
1 Is the hydropneumatic unit serviceable and if so where can I get spares or a replacement unit?
2 Can I change to the standard compensation spring set up?

Regards Graham

[teahead]

Yes, change out to a regular spring.

http://coilsprings.com/classic.aspx

https://slmarket.ipower.com/dev/custom-springs-for-your-mercedes-benz/

[dirkbalter]

I don't think the W113's have hydro pneumatic compensation springs. These are for the sedans, 108....
 

[MikeSimon]

I thought this was brought up shore time ago already. No Hydro-Pneumo in the SL. There is nothing to power that in the car.

[Benz Dr.]

It's like a big shock absorber so it's self energized.

I have a rear axle on my bench right now and I will have someone take a couple of pictures of how easily it is to remove the compensating spring with a hooked bar. I can't explain it that well so I think pictures will help.

[teahead]

Does it look like this?

[dirkbalter]

Does it look like this?

Yes, have one on my SEL too. But I don't think these are original to the SL's?

[MikeSimon]

If it is "hydro-pneumatic" and like a "big shock absorber" it needs to be pressurized with air or nitrogen. These systems used to be very popular for rear shocks on motorcycles. Somehow, there has to be a pressure line to the shock and a connection.

[ggdtr5]

Yes it is like the photos. My Haynes book says that there were two types fitted  to the SL’s a standard compensating spring and a hydropneumatic compensating spring.
My question is can I convert to a standard compensating spring?

Regards Graham

[teahead]

Yes it is like the photos. My Haynes book says that there were two types fitted  to the SL’s a standard compensating spring and a hydropneumatic compensating spring.
My question is can I convert to a standard compensating spring?

Regards Graham

Yup, you can. 

[ggdtr5]

Thanks teahead, what parts do I need?

[neelyrc]

There was a discussion on this subject about five years ago.  See here:

https://www.sl113.org/forums/index.php?topic=20673.msg148781#msg148781

Apparently a couple of members have fitted them to their cars.

[Shvegel]

Spring, Right side spring seat, 2 rubber isolators, 2 bolts for right side seat.  Only part that is SL specific is the spring.

[wwheeler]

So did the SL ever have the compensator?

I have a W111 and it has it and I am very familiar with it. It cannot be serviced by mere mortals and requires an expert to rebuild. It comes from the factory charged with nitrogen and is self contained. It is useful only for heavy loads in the trunk where it compensates and raises the height of the rear. No pumps, hoses, sensors or nothing. It is all self contained.  That is why it is on the bigger cars with large trunks and back seats. I wouldn't think an SL would benefit from that. They do not affect handling at all unless it has totally failed or you have a very heavy load in the back.

It can be absolutely switched out to the coil spring. I am sure there are kits to do so.

[WRe]

Hi,
afaik the hydro was installed in W108/111 cars but fitted also in others:
- https://nemigaparts.com/cat_spares/epc/mercedes/1/fg/113044/249/35/.
Here you find some technical information:
- https://vdhflipbooks.de/books/WHB/WHB1959-Band-2/index.html#349.
To install a spring you need additional rubber rings (left and right) and support bracket, pos. 88+89:
- https://www.sls-hh-shop.de/main/en/35-rear-suspension-35-a-rear-suspension-c-3_2346_68
- Here another vendor where you find MB spare part numbers too: https://www.niemoeller.de/de/w113/w113/B044/320/
- Useful information for comparison (change kit): https://www.niemoeller.de/de/w108/w108/B057/21/27.
The left side stays the same, except an additional rubber ring.
...WRe

[Shvegel]

Graham,
Found this in the attic of my garage.  I will never use it.  If you want it message me your address and I will send it out to you.

[ggdtr5]

Pm sent

[ggdtr5]

Ok, latest status

Removed my hydropneumatic compensator spring - it came out really easy and replaced it with a standard spring , I used a compression tool as identified in this forum consisting of a threaded bar through the left hand mount - it worked well.
I needed a new right hand bracket and two rubber mounts(bought from SLS in Germany) however, whilst the camber angle is better it is still negative and the rear end is still a bit low.
So I am going to look at the rear suspension. New springs (blue) were fitted by a previous owner in 2016 c/w 18mm upper mounts so I do not think the springs are weak however I plan change the rubber mounts , top and bottom. I have ordered 30mm top mounts as the difference in height between front and back is around 12 mm. hopefully this will raise the rear of the car and reduce the negative camber. I will also check the spring mounting plate - I believe there are three positions.- not sure which one it should be.
Once I have fitted the 30mm mounts I will update this post with the results.
Wish me luck🙏

Incidentally I found out , looking through the records of the car,  that the hydropneumatic compensating spring was fitted to my car by a previous owner in USA in 1992 and it came from a 280 SEL 4.5, He also fitted a 3.27 diff.

Regards Graham

[Tyler S]

Dont forget about the upper differential mount. It plays a key factor in camber. If it is collapsed then the diff drops down and induces negative camber. First photo is of a collapsed mount

https://www.sl113.org/forums/index.php?topic=806.0

[ggdtr5]

To close this post out

I fitted 30mm upper rear spring mounts and replaced the lower ones as well and the car is now sitting nice and level and I do not have any negative camber on the rear wheels.

I noted that the lower spring mounting plates were at position 3 (which is the lowest position) so I still have more adjustment on the camber if needed.

Very happy with the result 👍