My S500 rides like a cloud but I have noticed that it does not self level. The fluid level is normal and it's not bouncy. I added about 500 to 600 lbs in the trunk and it lowered about 3 inches and never came back up over 20 min of watching it with it idleing. I removed the weight and it went back up to normal. Any idea? It does not have ADS and the auto leveling arm is attached to sway bar. How will I know if the pump is bad. I've had it up on the lift to remove all weight and it still sits normal so I think the check valve is working. I have read that people have done that and it lowered the car.