The mysterious inards of a SLS accumulator
 

I changed out the accumulators on my wagon today. The rearend bounced like crazy going over small bumps. It would almost make a person seasick in the back seat.
I thought I would cut one open to see what was inside for my own interest and all the forum folks as well. There is a ring inside that holds a rubber diaphragm. On one side of the diaphragm is suspension fluid and the other is pressurized gas(not sure what kind of gas). When the diaphragm ruptures it fills the whole accumulator with fluid causing the rearend to bounce.

Rubber diaphragm down:
http://i35.photobucket.com/albums/d1...umulator01.jpg
Rubber diaphragm up:
http://i35.photobucket.com/albums/d1...umulator02.jpg

Cool. Gas is nitrogen I think.

What did you cut that open with? Thanks for the view inside. I've replaced 4, and at least now I can visualize the guts....

My sharp whits!:P

I used an angle grinder. It's really thick steel I was quite surprised.

Wow, so there's no way to test these spheres off of the car?

Fill it with oil and measure the volume it takes vs the volume the body displaces. If the diaphragm is intact the volume of oil will be relatively small.

Cool, I did the same thing with the engine mounts when I replaced them...

http://i3.photobucket.com/albums/y71...s/423502e0.jpg

Yes- take a rod with a blunt end and attempt to push the rod into the sphere. If it pushes down easily the sphere is no good. If it's difficult or you cannot the sphere is good. The volume of oil means nothing- a bad sphere may displace a small amount of oil but show little resistance and be worthless. You'd have to wait for some time for the oil to seep. Pushing a blunt rod takes only seconds anyways. A phillips screwdriver will work in a pinch- just be sure to push in the center.
http://i176.photobucket.com/albums/w...s/PJat6038.jpg

With a little bit of adaptation, you could replace these with Citroen spheres. The later ones use the same hydraulic fluid as the accumulators and they last 20 years. I've got some early ones that have lasted longer. And the older ones are rebuildable with parts still around. They come apart and can be re-gassed and reused for about 20 bucks.

I have several spares in my garage- no need to change nuttin...:D

If you have a dead one, can you send it to me so I can so some experiements? I re-gas the Cit ones and have built a set-up to do it.

I can probably regas the accumulators as well, although they look like some of the newer ones that are not made to be regassed.

I think the failure mode for these items is the diaphragm, which lets the nitrogen leak out. You can't disassemble the sphere (as with a Citroen sphere) and replace it - it's a welded unit. Adapting Citroen spheres might be interesting, as it would provide you with rebuildable parts in the suspension. But you still have the expensive struts to worry about...

I don't have any dead ones- I test them in the yard so i don't waste $ buying a bad one.

Have you ever found any good ones in the junkyard? I've only been able to find blown ones.

I wonder how the gas gets out. Isn't this mounted upright under the car? Even if it was sideways, you'd think some of the gas above the hole would remain in there...maybe its pressurized and when the diaphragm tears the pressure drops to near atmospheric and there's not enough "spring" left.