Hey guys, I just had my steering pump and steering box replaced and I was checking the fluids under the hood and I noticed that there is a reservoir for hydraulic fluid (located on the drivers side in front of the shock tower under the plastic cap in a semitransparent reservoir). Car in question is a 98 S500 with level ride but without ADS. I thought the hydraulic fluid was for the steering system (tandem pump), but while checking the fluids the steering fluid was ok, but the hydraulic fluid was bone dry. Did the tech forget to refill? Or is the hydraulic fluid for the rear leveling suspension? I don't see any leaks at the rear of the car, so why is the fluid low? Are the accumulators full of fluid? To refill, do I simply remove the dipstick and refill through that opening? I have read (in this forum) that if the accumulators were bad (i.e. fill of fluid) that I would be experiencing a very bouncy ride, however, the car rides beautifully.

All replies are much appreciated!

The reservoir you refer to is for the self leveling suspension, plastic jar type thing with a cap and a dip stick. ASD and ADS use the same I dont know where your fluid went, one or both of the accumulators could have punctured. It is a semi bouncy ride if you go over bumbs, the problem is if you drive too long without the spheres functioning it ruins the shocks which are about $440 ea. There might be just enugh oil but does not show up on dip stick, get some from your MB dealer and see what happens. I recall there is a line on the stick that says "full when loaded". the system can be bled thru a port on the controller near the rear axle. ADS provides similar operation to the front shock and rear by electrially controlling the rate of fluid flow depending on the setting.

You said the reservoir is bone dry which is not good at all. You probably just have enough fluid in the pump to keep the system working but you are so close to ruining the pump itself. You need to refill the reservoir immediately and start the troubleshoot process from there.

Pete, whats ASD? I know ADS is "Addaptive Dampening System".


Jim, what pump are you talking about? Power steering? The power steering reservoir is full and the steering feels fine.

I am fairly confident that my car does not take hydraulic fluid for the steering pump, which I have learned from a thread that I posted in this forum a few days ago. However, for w140s with ADS I think the hydraulic fluid is used for the steering pump as well as the ADS.