Disassembling and Assembling Rear Spring Strut
Disassembling and assembling rear spring strutTools
Information
Notes on repairing air-spring struts
Note:
As of a mileage of 200,000 Km it is recommended that the air springs be replaced per axle if there is damage to one air spring.
If the shock absorbers leak, the complete air spring strut is to be replaced. The oil of the shock absorber can damage the roller.
When depressurized, the air spring must not be twisted. There is the danger that the roller in the inside of the air spring will be damaged by bending or folding and thus significantly reduce the running time.
Air-spring strut
1. Before loosening the air lines in the installed state, check if the rolling boot is still filled with the residual pressure of approximately 3 bar.
To do this, press on the rolling boot of the air spring with your thumb. The rolling boot must give perceptible resistance. If no significant resistance can be felt, the air spring is depressurized and must be replaced along with the residual pressure retaining valve.
The greatest possible care and cleanliness, as well as perfect tools are important requirements for carrying out perfect repairs on air-spring struts. The general and basic rules of safety apply. These are specifically listed here again for repairing air-spring struts.
- Thoroughly clean the connection points and their surroundings before loosening them.
- Do not use fiber-shedding cloths.
- Do not take spare parts out of the packaging until right before installation.
- Only use lubricants that have part numbers.
- Carefully cover open components or close them if the repair work will not be carried out immediately.
- Do not use an impact bolter.
- Observe correct tightening torques.
Gaskets, sealing rings and bellows
Always replace sealing rings and bellows.
After removing gaskets, examine the contact surfaces on housings for burrs and damage.
Always loosen and tighten screws or nuts crosswise for mounting covers and housing.
Residual pressure retaining valve
ATTENTION:
Lowering of the vehicle when loosening the air line. The residual pressure retaining valve can become loose when loosening the air line.
^ The vehicle lowers on the side on which the line/the residual pressure retaining valve is loosened. Risk of squashing.
^ When loosening the residual pressure retaining valve, lift the vehicle on a platform lift.
^ Only leave the vehicle on the platform lift until a new residual pressure retaining valve is installed and the air-spring strut is filled.
The residual pressure retaining valve may only be replaced if:
1. Residual pressure retaining valve
2. Socket insert
- it was damaged during removal and installation,
- it was damaged while disassembling and assembling the air-spring strut,
- the sealing ring is faulty,
- it does not allow any more air to come out (valve jammed).
If the residual pressure retaining valve is jammed, the vehicle must be lifted for replacement on the platform lift and the wheels must be allowed to turn freely. It must not be compressed with an empty rolling boot.
Tools and materials
Tools for repairing air-spring struts
Torque wrench 2-10 Nm (1.5-7.5 ft lb.)
Torque wrench 60-100 Nm (44-74 ft lb.)
Socket wrench insert 3353
Arm bracket P 9630
Information
Overview of rear air-spring strut
Note: The components of the air spring -7- (figure shows component arrangement of rear air-spring strut), Items -2; 3; 4; 5- (figure shows rear air-spring strut), cannot be disassembled.
^ Always replace the complete air spring -7- (figure shows component arrangement of rear air-spring strut)!
Disassembling and assembling
Disassembling spring strut
ATTENTION:
The air-spring strut is pressurized with approximately 3 bar residual pressure. Never us an impact bolter to loosen the fastening screws. Do not bend over the mounting saddle during disassembly.
^ Risk of injury from the pressurized air-spring strut when loosening the screws.
^ Always unscrew the screws on the mounting saddle by one turn only, on alternating sides. During disassembly, allow the air to escape by tilting the mounting saddle slightly.
1. Clamp the air-spring strut on the lower mounting point (use aluminum protective jaws -A-!).
2. Loosen the fastening screws on the mounting saddle.
3. Carefully remove the mounting saddle over the residual pressure retaining valve in direction of arrow.
4. Remove spring-strut mount with socket wrench insert 3353 and arm bracket P9630.
5. Remove clamp.
Note:
When replacing the air spring, always replace the boot/bellows.
If the rolling piston slips out of the outer guide during disassembly, it must be correctly positioned again when assembling.
^ When sliding in the rolling piston, the roller must lie evenly between the outer guide and rolling piston (roll fold).
6. Push bellows downward and secure in this position (2nd worker required!). Grasp the rolling piston and remove it upward from the shock absorber by slightly turning to the left/right.
7. When replacing the air spring, push the rubber stop -1- out of the centering device.
8. Remove boot/bellows.
9. When replacing the shock absorber, remove the cap and fit it on the new shock absorber.
Assembling spring strut
Note:
When replacing the air spring, always replace the boot/bellows.
If the rolling piston slips out of the outer guide during disassembly, it must be correctly positioned again.
^ When sliding in the rolling piston, the roller must lie evenly between the outer guide and rolling piston (roll fold).
If the shock absorber is not replaced, the sealing ring must be replaced.
^ Make sure that everything remains absolutely clean. The smallest impurities can cause leakages.
^ Clean the contact surfaces of the sealing rings with a lint-free cloth.
^ Lightly grease sealing rings with Syntheso Glep 1 (ET No. 000.043.204.68).
1. Replace sealing ring on shock absorber -Arrow-.
2. Pull boot/bellows completely over the collar of the shock absorber so that it engages (small diameter downward, 2nd worker required).
3. Fit rubber stop (small diameter downward).
4. Position the air spring on the shock absorber. Grasp the rolling piston and push downward by turning it slightly to the left and right. If the rolling piston has slipped out of the outer guide, it must be pushed back in again while forming a circumferential uniform roll fold on the rolling boot -Arrows-.
5. Clean the surfaces -2- on the mounting saddle and on the air spring with a lint-free cloth. Replace sealing ring -1- on the air spring.
6. Align the air spring so that the residual pressure retaining valve is located close to the imaginary axis of symmetry (approximately 10� off-center) of the air-spring strut.
7. Fit bellows (large diameter up).
8. Fit spring-strut mount with socket wrench insert 3353 and arm bracket P9630.
9. Fit mounting saddle and while doing so align it so that the upper arm of the bearing points to the residual pressure retaining valve.
10. Fill the air-spring strut.
Checking the air-spring strut
Checking for leaks
1. Dip the filled air-spring strut completely into a water bath.
Note: Before fitting the air-spring strut in the vehicle, carefully blow out and dry all electrical connections and the residual pressure retaining valve with compressed air.
2. There must be no air bubbles rising in the water bath. If no air bubbles can be seen, the air-spring strut can be fitted in the vehicle.
3. If air bubbles appear in the water bath, the air-spring strut must be disassembled again. Replace all sealing rings again. Check the residual pressure retaining valve again visually.
4. Repeat the leak test in the water bath.