Where has all the fluid gone??
 

86 560SEL 53K

I've put 3 litres of MB hydraulic fluid in the suspension reservoir today. It's empty again. Where is it going?

I see no leakage up front. I've looked under the rear, although not really under, just what I can see from looking under the car and hands and knees and see no dripping.

Must I use MB hydraulic fluid or will any hydraulic fluid work?

Also, when the car is running, I hear a hissing from under the rear near the passenger rear wheel.

is the ride bouncy? if it is then likely the nitrogen has left the nitrogen chambers and the fluid is filling them, or it could be intering the crankcase through the system pump, check oil level and see it it is over filled, the hissing you hear is the fuel pumps running. personally i would only use mb fluid, but others may have suggestions on compatible fluids

ride is not bouncy, very smooth actually

following the car down the road yesterday it looked like the driver side rear wheel was slightly "squatted"

just checked the oil... it was right at the bottom of the upper red "thingy"

it's very possible that the fluid pump is leaking fluid back into the engine.those pumps are big money BUT i have had 100% success rebuilding them with a very comprehensive kit available for about $45

i've been able to take a better look with a light and crawl in under the car. there is wetness on the inner rear trailing arm and around the two nuts that attach the lines to the air cell. when i get some more fluid i plan to fill it up again, crawl under and see if i can tell where it's leaking. hopefully all i have to do i snug up the nuts

the passenger side is totally dry and both shocks are dry

according to my dipstick my oil is not overfilled which it should be if 3 litres of oil had drained into the crankcase

am i on the right track??

If you see wetness then you're probably in the right direction,,, on a side note,,, you getting alot of people blowing past you flipping you off? (oil misting on the car behind you)

Well, my theory didn't pan out as hoped. I put more fluid in the reservoir, started it up, looked back at the left side air cell expecting to see fluid escaping from the nuts at the lines to the air cell. Nothing leaking. HOWEVER, within a 15 minutes 1/2 a litre of fluid was gone.

Now i'm thinking you may be right about the pump leaking into the engine. But my dipstick is inconclusive. I turned the car off, let it sit for a few minutes and checked the oil. It appeared to be slightly overfilled, but the more time I let go by the oil level appeared to go lower, but still appears to be overfilled slightly.

What damage am I doing to the engine if hydraulic fluid is mixing with the oil? I'm not driving it until this mytery is solved.

no more suspension fluid loss after replacing seals in the pump. appeared that the rear seal was torn which allowed the hydraulic fluid to leak into the engine.

now i need to change the accumulators which have become too bouncy.

should the rear tires be straight up and down at normal ride level or is it normal to have a slight negative? camber? (/---\)