Testing Rear Accumulator

TESTING ACCUMULATOR ON REAR AXLE

Rear Axle





Control rod/connecting rod (55/7):
detach, attach at level control unit (3). Replace self-locking hexagon bolts and nuts, 10 Nm (items 1 and 18).

Lever (3a) on level control unit:
set to "emptying" position.

Oil drain hose:
put on oil drain plug (3p) on level control unit (3) (item 3).

Oil drain plug (3p):
open slowly and release pressure, collecting the oil in a clean container. Unscrew oil drain plug (items 4 and 5).

Pressure tester (038):
connect to level control unit with test hose (038g) (item 6).





Pressure lines (S1, S2):
disconnect, connect to left-hand and right-hand accumulator using open box wrench 116 589 00 17 00, 14 Nm. Seal with connector and bleed screw (item 7).

Pressure tester (038):
connect to right-hand accumulator (4) with test hose (038d) (item 8).

Engine:
start, stop (item 9).

Lever (3a) on level control unit:
set on "fill". The pointer on the pressure tester 126 589 14 21 00 must rise suddenly to a minimum value of 15 bar, and when the accumulator is new, to 23 ± 1 bar. Then set lever (3a) on level control unit to "emptying".

Oil drain hose:
attach, remove at the bleed screw.

Bleed screw on pressure tester (038):
open slowly and release pressure, collecting the oil in a clean container. Close bleed screw (item 13).

Accumulator (4):
The test sequence is the same for both accumulators.

Pressure oil system:
fill.

Oil level:
check in oil reservoir (2) and if necessary fill up with hydraulic oil 000 989 91 03 using funnel 126 589 12 63 00 (item 19).

Note
The following parts are required for testing:





Pressure tester with connection and union nut with sealing ring (038a), test hoses (038d) and (038g), 2 bleed screws (038n) and 2 couplings (038f).

Insufficient gas pressure results in an abnormal pressure increase during deflection. This will be noticed by stiffening of the suspension and may under certain circumstances lead to damage of the suspension units. Furthermore, a stiffer suspension may cause the damping force of the spring strut to become too low, resulting in increased vehicle roll or vibrations when driving through alternating corners.

Testing Model 124





1 Unbolt self-locking hexagon nut (7a) and detach connecting rod (7).





2 Set lever on level control unit to "emptying".





3 Attach oil drain hose (061) to the oil drain plug (3p) on level control unit.

4 Slowly open oil drain plug (3p) and release pressure. Collect oil in a clean container.

5 Unscrew oil drain plug (3p) on level control unit.





6 Connect pressure tester (038) to level control unit (3) with test hose (038d).





7 Connect pressure line (S1, S2) on left and right accumulators (4) using open box wrench. Seal both pressure lines with coupling (038f) and bleed screw (038n).

Testing Right-Hand Accumulator





8 Connect test hose (038d) of pressure tester to right-hand accumulator (4).

9 Start engine and allow to idle.





10 Set lever (3a) on level control unit to "fill", while watching the pointer on manometer.

Set value:
The gas pressure of the accumulator is indicated when the needle of the pressure gauge rises suddenly to a pressure value of 15 bar and when the accumulator is new to 23 + 1 bar. This sudden rise is caused by the oil pressure when the oil pressure exceeds the gas pressure.





11 Set lever (3a) of level control unit to "emptying" and turn off engine.

12 Attach oil drain hose (061) to bleed screw (038n).

13 Slowly open bleed screw (038n) and release pressure. Collect oil in a clean container.





Testing Left Accumulator

14 Connect test hose to left accumulator and repeat steps 8 to 13.

15 Disconnect pressure tester. Screw oil drain plug into the level controller. Connect pressure line to the accumulators using an open box wrench, 14 Nm.





16 Pour collected oil into the oil reservoir (2) through the funnel (060).

Note:
Re-use clean oil only.

17 Fill pressure oil system. Procedures

Model 124





Attach connecting rod (7) in lever of level control unit and tighten new self-locking hexagon nut, 10 Nm.

19 Check oil level in oil reservoir (2) with engine stopped and correct if required. When system is in operational condition, the oil level in ready-to-drive condition should be between the markings "max" and "min". When the vehicle is loaded, the oil level will then be below the "min" mark (no longer visible on dipstick).