Suspension: Adjustments
ADJUSTING VEHICLE LEVEL ON REAR AXLE OF VEHICLES WITH LEVEL CONTROL
Preliminary work:
Positioning of wheels.
Check and adjust vehicle level on front and rear axle. [1][2]Component Tests and General Diagnostics
Vehicle:
to repair place vehicle on sliding supports. Load rear of vehicle. Check level in supply tank, top up if necessary.
Engine:
run engine for approx. 1 minute at approx. 2000 rpm.
Level controller:
shortly actuate with hand, to position "filling" and then to "emptying" (fig. 4).
Vehicle level on rear axle:
determine by measuring position of semi-trailing arm. Measuring device 107 589 02 21 00 or 107589 Ol 21 00.
Rear of vehicle:
is to be pulled down with pulling device 201 589 11 31 00 until control point has been reached (fig. 4). Vehicle can also be loaded with weights up to control point.
Level controller:
retain middle position with pin (fig. 5). When adjustment is correct pin must enter with little effort.
For control point adjustment:
Connecting rod (7):
detach, attach, check ball joints (fig. 4, 7).
Control point (see table):
adjust, by adjusting connecting rod properly. The connecting rod must fit, without excessive pulling and pressing, over the controller fixed in middle position (fig. 5).
CAUTION!
Use correct bore (fig. 7). Remove pin for middle position after adjustment.
Rear of vehicle:
unload, or remove pulling device, if installed (fig. 9).
Test drive:
perform with test load, and check vehicle level again (fig. 10).
Lighting system, front:
adjust (82-040).
SPECIAL TOOLS
Equipment (self-made)
Weights for loading vehicle (e.g. for measuring the vehicle level on vehicles with level control and for fuel level compensation).
2 x 5kg
5 x 10kg
5 x 20kg
Conventional Tools
Sliding plates for rear wheels (1 m long) e.g. Beissbarth P1/109, Bosch EFAW 406.
Checkinq And Adjustment Values For Vehicle Level When Laden
Permissible difference of vehicle level measured between left and right side of vehicle:
with measuring dev. approx. 8 mm
with tape measure approx. 15 mm 1)
1) Measured from center of wheel to edge of fender well.
Location Of Connecting Rod On Lever Of Level Controller
Bore "a", rear axle without anti-squat geometry.
Bore "b", rear axle with anti-squat geometry
Note
The level control system on the rear axle is a hydro-pneumatic auxiliary suspension which is automatically connected at a given deflection. On sedans, for example, the level control begins to operate starting from a load of two persons on the front seats and approx. 40 kg luggage in trunk. The control point for the loaded vehicle is the respective level which meets the projected level of the respective vehicle.
A prerequisite for correct functioning of the level control, as well as for good driving comfort and optimal driving characteristics is a vehicle level set according to specifications both in curb weight conditions as well as under load.
In curb weight condition the rear end of the vehicle is supported by the rear springs and the basic pressure in the suspension elements only. The basic pressure is maintained by drain valve in level controller, independent of the respective position of lever.
CAUTION!
A rear end which is too low in curb weight condition should never be set higher by adjusting the connecting rod of the level controller.
The result would be a continuously and excessively high level under load. The results would be poor driving characteristics, there would be oil flow and knocking noises during deflection, and the ball head would be too high for operation of a trailer.
Under high load, as well as during acceleration, the max. pressure in suspension elements limited by level controller would be additionally attained, so that the opening noise of the pressure relief valve would be constantly heard during such driving conditions as a whistling and knocking noise. Therefore, if the vehicle is too low in curb weight condition, corrections on rear springs are required.
A prerequisite for evaluating the curb weight level is, however, that the full basic pressure in the suspension elements is available.
For this reason, prior to measuring the vehicle level (semi-trailing arm position), the level controller must be momentarily moved upwards into "filling" position and then downwards into "emptying" position, with the connecting rod disconnected and the engine running.
Before beginning with the checkup of the vehicle level on the rear axle with a load, check level of curb weight vehicle, and correct if necessary. [1][2]Component Tests and General Diagnostics
Previous Jobs:
1 Place vehicle on measuring rig.
2 Check curb weight vehicle level, i.e. prior to checkup and adjustment of level control point, the level values of the rear axle at curb weight must be within the tolerance.
3 Check oil level in supply tank, top up.
4 For checking and adjusting the level control point use measuring instrument (02) 107 589 Ol 21 00 for semi-trailing arm suspension or 107 589 02 21 00 for semi-trailing arm suspension with anti-squat geometry. There are two possibilities for loading the vehicle for adjusting the control point.
a. Load Rear End With Weights
- Place weights in trunk until the level is 10 mm below level control point.
- Disconnect connecting rod from level controller with the engine running at approx. 2000 rpm, and induce pressure on the level controller (push lever on level controller up to position "F") until the measuring device indicates the specified level value for a loaded rear axle (control point).
b. Pull Down Rear Of Vehicle With Pulling Device 201 58911 31 00
- Attach pulling device.
a) On vehicles without trailer hitch attach and lock (arrows) the upper cross member of pulling device (040b) via adapter bolts (040a). Bolts fit openings, sealed with rubber grommets, in frame side member. Attach lower cross member (040c) with spindle (040d) to pit or hoist.
b) On vehicles with a trailer hitch on which the openings in the frame side member are covered up by the trailer hitch. Attach pulling device with two additional chains (041) to the inner eyelets on trailer hitch. Attach lower cross member (040c) with spindle (040d) to pit or hoist.
- Pull down rear end of vehicle, until the measuring device indicates the predetermined level control point.
5 Check middle position of level controller (84) by inserting the 4 mm retaining pin. If the retaining pin (015) cannot be inserted in the connecting rod (84a) or only through pulling and pressing, adjustment has to be carried out.
6 For loosening connecting rod on level controller, always unscrew hex. nut on lever of level controller. If required, hold ball pin in position with an open-end 10 mm wrench. Never pull ball pin out of ball socket.
Check ball joints of connecting rod.
7 Fasten connecting rod to the correct bores.
Bore "a" is for swing axle without anti-squat geometry.
Bore "b" is for swing axle with anti-squat geometry.
Note
Following adjustment work on level controller, it is absolutely necessary to remove pin. Failure to do so, causes severe damage to the level controller!
8 Starting 08/85 the rear axle center part will be elastically suspended. The level controller is therefore moved from the left to the right side, and will at the same time be replaced by the level controller of model 124. The testing and adjusting methods have not changed.
9 Remove pulling device.
10 Carry out test drive with test load. Check vehicle level.
Before each check of vehicle level, run engine for about 1 minute at approx. 2000 rpm.
11 Adjust headlamps.