Not trying to steal thunder... simultaneous post.

The SLS (hydro pneumatic suspension) on the 123 wagons all function in the same manner with only variation in the 123 wagon chassis SLS being the location of the hydraulic reservoir. Later model 123s (1985) have the reservoir on the left side of the engine, earlier models it is on the right (turbo) side of the engine.

The system is made up of the following components: timing chain driven hydraulic pump (located in the engine head), hydraulic reservoir, position sensing valve, hydraulic struts (2, located inside the rear springs), accumulators (2, located below the cargo area and near the rear springs) and all associated hydraulic tubing.

The engine driven pump supplies hydraulic fluid under pressure (about 130 to 185 bar or 1800 to 2600 psi) to the position sensing valve where, depending on the position of the vehicle body in relationship to the rear wheels, pressurized fluid is admitted to or released from the hydraulic struts and accumulators by the position sensing valve.

Basically, if the car body is lower (ie loaded), fluid is admitted to the struts and raises the body until the valve reaches its shutoff, or bypass point where the fluid is returned to the reservoir. If the car body is too high, fluid is released, lowering the body until the valve's bypass point is reached.

The system's accumulators (two metal spheres approximately the same size as a softball) function as the load supporting devices. Inside each accumulator there is a rubber bladder which is charged with high pressure nitrogen. Hydraulic tubing connects the struts to the accumulators so that when the position sensing valve admits fluid to the struts, it passes through the struts to the accumulators, pressurizing (by compressing the bladders) them until pressure in the accumulators supports the vehicle weight (and load if any). Once this equilibrium is reached, the system's pump continues to pressurize the system and raise the vehicle until the position valve reaches the bypass position. Conversely, if the pressure in the accumulators is greater than what is needed to support the load (ie weight has been removed from the cargo area and the body is too high) the position sensor will release fluid to the reservoir, lowering the body until the bypass position is once again reached.

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Never a dull moment at Berry Hill Farm.