Bleeding, Draining and Refilling of Hydraulic System
Hydraulic system - Draining and refillingModel 129
Draining pressure oil system
- Unscrew Bolt (50a) on distribution valve (50), by approximately 1 turn (Position 1).
Note: The Allen bolt (50a) was replaced by a hexagon bolt in 09/90.
- Plug oil drain hose onto fluid drain plug (3p, 6p) on the level controller (3, 6).
Caution: Ensure that the front wheels are pointing straight ahead.
- Open oil drain plug (3p, 6p) slowly and drain the fluid into a clean container. Then reclose the drain plug (3p, 6p), 14 Nm (Position 5).
Filling pressure oil system
- Put level control switch into "normal level" position. The red indicator lamp in the switch must not light up.
- Fill hydraulic oil into the oil reservoir (2) with funnel 126 589 12 63 00, until the oil level is between the "min." and "max." marking on the oil dipstick.
- Press lever on level control unitinto position "Fill" (No.8).
- Allow engine to run at approx. 2000 rpm, until level of vehicle visibly rises at front and rear axle. Switch off engine. Pay attention to oil level in oil reservoir (note information No.9).
- Screw screw (50a) into distributor valve (50).
- Install connecting rod/control rod (54, 55) on level controller lever (3, 6). Replace self-locking hexagon nut, 10 Nm.
- Start engine, allow to run at approx. 2000 rpm.
- Fill pressure oil system until the normal vehicle level is reached, whilst noting the oil level.
Caution! If during repair work the oil reservoir (2) has been emptied or the pressure oil pump (1) replaced or the high pressure extending hose (4) has been replaced or unscrewed, the pressure oil pump must be bled.
Special Tools:
Caution! Use a line wrench for tightening the pressure lines, and under no circumstances a normal open~end wrench in order to avoid damage to the line connections. Use special tool to improve access to individual line connections.
Only use solid copper sealing rings of the specified dimensions for the banjo bolts.Always replace sealing rings.
Note: The pressure oil pump has its own lubrication, i.e. the oil delivered acts simultaneously as lubricant.
Scope of work
Draining pressure oil system
Version Installed Up To 8/90:
1 Unscrew bolt (50a) approximately one turn using 4 mm Allan key.
Version Installed Since 8/90:
Note: In 9/90 the Allen-type pressure supply bolt (50a) was replaced by a 10 mm hexagon bolt.
2 If connecting rod/control rod is fitted. Remove connecting rod/control rod (54) at the lever of the level control unit (6). If necessary use open- end wrench to hold hinge pin in position.
Caution! Ensure that the front wheels are pointing straight ahead.
3 Slowly open oil drain plug (6p) whilst collecting the oil in an oil reservoir (2). Then retighten oil drain plug, 14 Nm.
4 If connecting rod/control rod is fitted. Remove connecting rod/control rod (55) at the lever of the level control unit (3). If necessary use openend wrenchto hold hinge pin in position.
Version Installed Up To 9/92:
Version Installed Since 9/92:
5 Plug the fluid drain hose (061) onto the level controller's (3) fluid drain plug (3p). Slowly open the drain plug (3p) and ailow the fluid to drain into a clean conainer. Then reclose the drain plug, 14 Nm.
Filling pressure oil system
(except for USA model)
6 Move level control switch (S77) into "normal level" position. Red indicator lamp in switch must not light up.
All models
7 Use funnel with strainer (060) to fill oil reservoir (2) with oil, until the oil level is between the "min." and "max." markings on the oil dipstick.
Note: Only re-use clean oil.
Front Suspension:
Rear Suspension:
8 Move lever (6a, 3a) of level control unit on front and rear axle into position "Fill".
F = Fill
L = Drain
9 Allow engine to run at approx. 2000 rpm until the level of vehicle rises visibly at front and rear axle. Note oil level in oil reservoir.
Note: The hydraulic system is not fully charged until the vehicle's suspension has extended to its maximum height. This procedure may be accompanied by whistling and bumping noises.
The bolt (50a) in the distribution valve (50) must be open while the system is being charged (Position 11).
10 Switch off engine.
Version Installed Up To 8/90:
Version Installed Since 9/90:
11 Screw bolt (50a) into distributor valve (50).
12 Mount the linkage rod/control rod (54, 55) on the lever on the level controller (rear suspension), or on the lever on the torsion bar (front suspension), 10 Nm.
13 Start the engine and let it run at about 2000 rpm.
14 Charge the hydraulic system until the vehicle reaches its normal ride height. Monitor the fluid level continuously during this procedure.
When engine is not running, oil level in oil reservoir must be between the markings "max." and "min.".
Caution! If during repair work, the oil reservoir has been emptied or the pressure oil pump replaced or the high pressure extending hose is replaced or unscrewed, the pressure oil pump must be bled. For this step, when the engine is running the high pressure extending hose disconnected at the steel line (P) must be held in a container, until no bubbles appear in the escaping oil.
Then repeat the work steps Nos. 6-14.
Note: After charging the hydraulic system, discharge the remaining air from the system by taking the vehicle for a test drive on an undulating, uneven road sunface. Then recheck the fluid level (Position 14).