Originally Posted by Douglas.Sherida

The accumulators do not need to be under positive pressure, they just need a sealed system that is completely filled with hydraulic fluid. Think about how the rear end works.

99.99% of the time the SLS valve is closed. It only opens (in either direction) when the car is loaded up or when that load is removed. The response time of the valve (and the pump) is far too slow for it to cycle open to adjust to road bumps. Therefore, you can think of the actuator/accumulator as a closed system. Its not possible for there to be negative pressure in the accumulator lines, just neutral and positive. It is the job of the accumulator to dampen road bumps. So long as the lines from the valve to the accumulators (through the actuators) are completely filled with hydraulic fluid, they will do their job.

The ideal setting would be to have the SLS set perfectly neutral at rest on the springs. In practice it may be easier to set the SLS to slightly lift the back off the springs, but only a very little (1/4 to 1/2 inch at the rear wheel wells). Over-compensating for weak springs by setting the ride height with the SLS is just putting unnecessary pressure on the valve, actuators and accumulators.

What I am suggesting to the original poster is that the SLS valve ride height is set below the spring height so that the valve is open to bleed off pressure from road bumps (bouncy) and load.



We'll never know that. I can't quote the FSM, but my 22 year old wagon (with 22 year old springs) drops less than an inch when the SLS valve is removed. If you weren't specifically looking for the drop (laying under the car), you'd never notice it (as an overnight sag). If you have a noticeable sag, you have bad springs.