Lifetime Premium Member
Date registered: Oct 2002
Vehicle: 1967 250 SL, 1963 220Sb
Location: Los Angeles / Altadena
Mentioned: 3 Post(s)
Quoted: 134 Post(s)
It's the rear suspension. It consists of a hydraulic pump driven by the engine that recirculates hydraulic fluid to the rear suspension and back to the front tank contentiously. There is a leveling valve that adjusts the ride height of the rear end based on where the car is sitting. For example, (using a US W123 station wagon) you have the car turned off on level ground and the car is level. You open the lift gate and 3 fat men sit on the back sill of the car. The car is no longer level. You start the car and the valve is now in a position where it knows that the suspension is too low so the valve sends more fluid to the hydraulic struts raising the car to a level position. Then the three fat guys get off the back of the car, that changes the positioning of the valve and it lowers the fluid to the hydraulic struts, again making it level. In between the valve and the hydraulic struts are hydraulic accumulators (spheres). These are spheres with a diaphragm - on one side of the diaphragm is nitrogen (I think) and on the other side hydraulic fluid. The diaphragm is not rigid - if you were to poke on it (through the hydraulic fluid opening) with the eraser side of a pencil you would feel the diaphragm and it would give a little. This is what makes the ride smooth. When an accumulator fails it is because the diaphragm has broken, meaning there is NO give in the fluid pressure. So if you go over a bump the suspension immediately responds by first sensing that the car is too low and adding pressure, then sensing that it is too high, relieving pressure. The result is that the back of the car can kind of jolt / hop when going over a speed bump. It's unpleasant. The jolt will only be on the side of the car that has the failed diaphragm.
The common failure points of the SLS are the valve and the accumulators. The valve will start to leak and it can be rebuilt (and it is not expensive to rebuild it). The accumulators you replace.
One of the discount auto places on-line lists the price for an accumulator as $110. The price for the hydraulic strut is $239. If you want to look at other prices, go to autohausaz.com and put in for your car search a 1985 Mercedes 300 TDT (it won't recognize the older non-US 114/115 car). The click suspension. Then click the part you are wondering about.
You replace the struts if they leak. You replace the accumulators if you get a big bump when you drive over a speed bump. You rebuild the valve the car sags overnight or otherwise just doesn't level itself.
Then in the front of the car I have no idea what you do -- my car never had issues in the hydraulic pump or tank.
It's a really nice system and provides a really nice ride. Very important for a car that will have varying loads in the back end...
Currently: 1967 250 SL, 1963 220Sb, 1965 300SE Lang, 1971 280SE parts car, 1972 Alfa GTV, 1965 Alfa Duetto, 1993 BMW R100R
Past: 1971 250 C, 1985 300 TD, 1967 250 S, 1968 280 S,1981 300 D, 1982 280CE, 3 Facel Vegas, Borgward Isabella Coupe, Alfa 2600 Sprint, Volvo P1900 (yes), numerous less interesting Volvos, ...