Since I owned my car I had rear suspension and ride issues. some times the car ride great and other time is flat out horrible. I am finally close to giving up and buying new shocks and new cells. Before I spend the money I was wondering if someone can provide me with a testing process to determine the problem before I can invest in new($$) shocks. I searched through the archives but could not find a clear answer.
My questions are:

How would you test if the pump is in working order?
How would you test if the air cell are in working order?
How would you test if the control valve are in working order?
How would you test if the air cell are in working order?

The air cell has 30,000 miles on them. The car has 143,000 miles. The ride height is fine but the tires sag a little. If you bounce the back it is soft but not too much movement.

Any help will be great.

Stevebl any ideas?

Well, a handful of questions have been hanging here, so I will take a shot:

Check the fluid level in the reservoir. Should be in the mark on the little dipstick.

To check the system, measure the height of the rear of the car, then load the trunk with soem heavy things, (bags of mulch, friends, etc). Start the car and see is the car returns to the same height.

To test the valve, try manually moving the actuator while the car is running. If the car moves up and down, it is doing its job. If not, you know something is not working, not necessarily the valve.

When my cells failed, opening the bleed screw on the level control valve resulted in a foamy fluid coming out. This may help you to check the cells. If you get foam, at least one cell is bad.

I don't know how to check the pump, other than looking at the reservior while the car is running and observing fluid moving around. Maybe someone else has a hint on that.

My car has 150K miles almost, and all that has been done is replacing the cells, and repairing the hose that wraps around the engine, when it wore through. Maybe you will have this kind of luck.

Take a look at these things, and post some more questions. I will try to help you out.

Good luck!

__________________
1989 560SEL (172k)
1989 325IC (122K)
2004 Suzuki Volusia LE (3500 miles)
2005 Yamaha Road Star (20 K miles)

I have a '84 500SEL with Full hydropneumatic suspension. When the car suddenly started acting up, I came to this forum and got nowhere. No help whatsoever!! I finally solved the problem myself by discovering that the filter in the suspension system was CLOGGED. A lousy $2 filter was all my problem. Although your car only has this suspension in the rear, it must have a filter. Find it and replace it. Wouldn't hurt to flush the hydraulic oil(special oil available from the dealer- I bought it in CA for $6 a bottle from parts house). Then, see if you still have problems. Hard ride is the gas cells themselves, no big deal. Shocks usually don't go bad, mine are 18 years old and 300,000 miles-still perfect! Good luck, let me know how you make out. If you can't find the location of the filter or filters, (one may be a tiny screen type, which looks like the old filters in a carb) I'm not sure, I'll look in the factory manuals, I have a full set.
Woody

The filter is inside the resevoir bottle, unscrew the cap and there it is, the return line dumps directly into the filter.

__________________
Mike Tangas
'73 280SEL 4.5 (9/72)- RIP
Only 8,173 units built from 5/71 thru 11/72

'02 CLK320 Cabriolet - wifey's mid-life crisis

2012 VW Jetta Sportwagon TDI...at least its a diesel

Non illegitemae carborundum.

Mike, I have a paper filter inside the reservoir also, but there is a second one in a valve that cloggs up. You may or may not have this one, however if there is a second one , you will need to find it as this the culprit.

Thanks for the replies. I have changed the filter around 10,000 mile ago. It was dirty. I also bled the line about the same time and the oil was foamy!!! The reason that I thought that it couldn't be the cells because I changed them 30,000 miles ago. The recommendation on this site is to be change them every 100,000 miles. I was thinking that if the shocks are bad they would shorten the life of the cells?

where the other filter would be? Inside the height control valve in the rear? Is it blocked? It make me wonder because the car sometime ride perfect specially when i don't drive it for two to three days? other times it is just bad!!!

I am going to test couple of more things before i invest in new shocks and cells. Any other thoughts would be great.

Thanks

On my valve, which is different, you had to remove a bolt and it revealed the tiny filter. IF you are having erratic behavior, and there is a filter in that valve, which is likely, you can blow thru it with a can of air, etc. and that will make it okay for a month or so while you find a new one. My filter had to be made at some factory in Germany. Good luck.

I am going to check and see if there a filter in the control valve. I will keep everybody posted. Thanks for all of the replies.

I just hate to spend the money and don't fix the problem. Some one suggested to me that I need to change the system to regular shocks and spring but I really don't want to do it. I want to keep the car original. Will see what happens.

Well I finally gave up and bought new shocks and air cells as well filter and oil. Overall the car rides better but I still have the erractic ride problem. My thoughts that it could be one thing which is the control valve. How can I be sure that it is the control level. What specific test is there? I noticed that it take a while for the car to adjust height when loaded. Any comments or opinons will be great.

I have 182k on my '88 560SEL I started replacing parts on my rear susp. about a year ago, I took advice from the forum and started with the Cells, replaced no fix problem, then the height valve located at rear (I did not notice any filter on valve BTW), replaced no fix problem, then I replaced the rear shocks (OEM Boge) not cheap, no fix problem, then the filter (I think this one is out of order), no fix the problem, I have just ordered a new pump will be here in a couple of days, as through trial and error method I have replaced almost all components, except for the rear springs which I have new ones in the garage need a spring compressor for those, and spent many large amounts of money. My two cents worth is spend a few $$ and get it diagnosed, then fix only what you need.

___________________________

'88 560SEL 182k Desert Taupe w/Brown

Hoopster,

What Symptoms did you car have that you started to change the suspension components? riding low? rough ride, etc... I see that I might be going the same path as you and it will be sad to not fix the problem after spending all that money.

The rear was sitting very low. Obvious the rear suspension was not working. I have been able to find most of the parts, from discount sources like www.performancemotorcars.com and ebay. I figure if I can buy the part cheap to just replace it. The pump I bought on ebay last week (item number 2402062937) for $235 new. The shocks same thing found new on ebay for $250 for the pair. If the pump does not fix it the only thing left to replace is the high pressure line. I had no question my susp. was not working as my wife says "it looks like a lowrider".