Hydraulic Oil Pump & Leveling Valve

NOTE: These tests can only be performed on a ready-to-drive vehicle. Check leveling valve for leaks during test. In case of leaks on valve housing parting surface, install new "O" ring.

Fig 1: Mercedes-Benz 300Td Level Control Rear Suspension System

Courtesy of MERCEDES-BENZ USA

1. Make sure that hydraulic oil is cold before starting test. Disconnect connecting bar at leveling valve lever. Tighten leveling valve housing screws.
   CAUTION: Do not loosen clamping screw retaining lever on valve control shaft.
2. Attach an oil drain line to bleed screw and release pressure in system by opening bleed screw. Remove bleed screw and attach pressure tester (126 589 02 21 00) directly to leveling valve via 3 or 4-way distribution fitting.
3. Push leveling valve lever up into filling position. Run engine at idle (800-1000 RPM) for a short time and observe pressure reading on tester. Pressure should read 1885 psi (132.5 kg/cm² ) minimum.
   NOTE: Perform this test quickly to avoid damage to components.
4. Turn off engine. Move leveling valve lever down to return flow position and observe base pressure reading. After a stabilization period of 5 minutes, repeat test procedure. Leave pressure tester connected at least 4 hours and observe.
   NOTE: Base pressure must not drop after the stabilization period. This also applies to extended periods, such as overnight.
5. Bleed base pressure at bleed screw, disconnect tester and install bleed screw. Fill level control system by running engine at medium RPM's and pushing leveling valve lever up into filling position for approximately 30 seconds.
6. Turn off engine. Reconnect connecting bar at leveling valve lever. Check reservoir oil level. Oil level should be between "Max." and "Min." for unloaded vehicle, "Min." for loaded vehicle.