Ⅳ. Air Suspension Maintenance Instructions

4.1 Vehicle Condition During Maintenance

When performing maintenance, the vehicle should be parked unloaded on a clean and level surface, preferably over a maintenance pit. Engage the parking brake and chock the wheels. Depending on the repair work, use suitable jacks or supports to lift the frame to an appropriate height, and decide whether the tires need to be removed.

4.2 Replacing Shock Absorbers and Rubber Bushings

4.2.1 Replacing the Shock Absorber

4.2.1.1 Remove the bolts connecting the shock absorber to the guide spring bracket and the spring seat, then take off the shock absorber.

4.2.1.2 Install a new shock absorber and tighten the bolts to the specified torque (see Appendix 1). If the self-locking nut is ineffective, replace it with a new one.
(This requirement applies to all fasteners in subsequent maintenance instructions and will not be repeated.)

4.2.1.3 After replacing the shock absorber, drive the vehicle for 1–2 hours, then check for oil leakage and ensure all mounting bolts are securely fastened.
(Note: The shock absorber may become very hot during prolonged operation. Do not touch it by hand.)

4.2.2 Replacing the Shock Absorber Rubber Bushings

4.2.2.1 Remove the shock absorber (see 4.2.1.1).

4.2.2.2 Use a bushing service tool or a press to remove the damaged or worn rubber bushings. Clean the bushing holes thoroughly. Check that the mounting ring is undamaged and has no cracks at the welds; otherwise, replace the shock absorber.

4.2.2.3 Press in new rubber bushings. The bushing should be centered symmetrically within the mounting ring (the protrusion length on both sides should be equal).

Note: When pressing the bushings, lubricate with solid vaseline or soapy water. Do not use oil-based lubricants or brake fluid, as they may damage rubber parts. The same rule applies to all subsequent bushing replacements.

4.2.2.4 Install and inspect the shock absorber (see 4.2.1.2 and 4.2.1.3).

Note: Shock absorbers and air springs are matched according to suspension models. Always use the correct type; otherwise, the air suspension’s performance and lifespan will be reduced, and premature damage may occur.

4.3 Replacing the Load Air Spring

4.3.1 Use a jack or support to lift the frame approximately 90 mm higher than the normal suspension height.

4.3.2 Deflate the load air spring: mark the position between the height valve vertical rod and its connecting sleeve, loosen the clamp, and turn the height valve balance lever downward to release the air.

4.3.3 Remove the damaged air spring by unscrewing the upper mounting nut, air pipe fitting, and lower base bolts.

4.3.4 Install the new air spring:

First, secure the base of the air spring onto the guide spring with bolts.

Then, fix the upper bolt to the upper air spring bracket with a nut.

Apply sealant or PTFE tape to the air pipe fitting threads before installation.

Tighten all bolts to the specified torque (see Appendix 1).

4.3.5 Restore the height valve vertical rod to its original position and tighten the clamp.

4.3.6 Remove the jack or support.

4.3.7 Start the engine and allow the system pressure to reach the compressor cut-off point. Check for air leaks and confirm that the air springs inflate normally (normal operating pressure: 0.6–0.8 MPa).

4.4 Height Valve Adjustment, Inspection, and Replacement

4.4.1 Height Valve Adjustment

4.4.1.1 During maintenance, if the suspension height deviates from the design value by more than H ± 5 mm, and other causes are excluded, adjust the height valve to restore the correct suspension height (see Section 2.6.2 for adjustment procedure).

4.4.1.2 After adjusting the suspension height, check the axle alignment. If alignment is incorrect, identify and fix the cause; if correct, proceed with the following steps.

4.4.1.3 Adjust the length of the vertical rod and tighten the clamp to the specified torque (see Appendix 1).

4.4.1.4 Supply system air pressure of 0.6–0.8 MPa and verify that all air springs inflate properly to the correct suspension height without leaks.

4.4.2 Height Valve Inspection

This procedure checks whether the height valve is functioning correctly and helps avoid unnecessary replacements.

4.4.2.1 Ensure system air pressure is 0.6–0.8 MPa.

4.4.2.2 Mark the connection between the vertical rod and connecting sleeve, loosen the clamp, and separate the rod from the sleeve.

4.4.2.3 Rotate the height valve balance lever upward and hold for 10 seconds; the air springs should inflate and the body should rise.

4.4.2.4 Move the lever to the neutral position; the valve should close—no inflation or exhaust occurs.

4.4.2.5 Rotate the balance lever downward and hold for 10 seconds; the air springs should deflate and the body should lower.

4.4.2.6 Move the lever back to neutral again; the valve should close completely.

4.4.2.7 Reconnect the sleeve and vertical rod at the marked position, tighten the clamp to the specified torque (see Appendix 1), and verify the air springs inflate to the correct height H.

If the valve does not perform as described, it is defective and must be replaced.

4.4.3 Height Valve Replacement

4.4.3.1 Support the frame with a jack or stand, keeping the vehicle near normal ride height.

4.4.3.2 Mark the vertical rod and sleeve connection, loosen the clamp, separate them, and turn the valve lever downward to release the air. Mark the air inlet/outlet pipes, disconnect them, and remove the height valve mounting bolts.

4.4.3.3 Install the new height valve in the original position, tightening to the specified torque.

4.4.3.4 Reconnect the air lines according to the marks (apply sealant or PTFE tape). Connect the outlet (to air spring) first, then the inlet.

4.4.3.5 Adjust the balance lever length to match the old valve, reconnect the vertical rod, align to the mark, and tighten the clamp.

4.4.3.6 Supply air pressure of 0.6–0.8 MPa to restore normal ride height, then remove the jack or support.

4.4.3.7 Check for air leaks with soapy water, especially at newly connected fittings, and confirm that the suspension height is correct. If not, readjust per the height valve installation procedure.

4.4.4 Replacing the Connecting Sleeve

After prolonged use, the connecting sleeve may age and need replacement.

4.4.4.1 Follow the same steps as height valve replacement.

4.4.4.2 Mark the vertical rod, loosen the clamp, and remove it. Deflate the air springs, detach the connecting sleeve from the lower bracket or balance lever, noting the direction of the pin and lever.

4.4.4.3 Install the new sleeve in the same direction, attach it to the lower bracket, insert the vertical rod to the marked length, and tighten the clamp to the specified torque (see Appendix 1).

4.4.4.4 Follow steps 4.4.3.6 and 4.4.3.7 thereafter.

4.5 Replacing the Relief Valve

Remove the old relief valve and install the new one in the direction of airflow indicated by the arrow on the valve body. Check valve operation per the air suspension maintenance requirements. After installation, reconnect the inlet and outlet fittings, pressurize the system to 0.6–0.8 MPa, and check for leaks.

4.6 Replacing the Guide Spring and Rubber Bushings

4.6.1 Replacing the Guide Spring

4.6.1.1 Support the frame with a jack or stand, shut off the air supply, and deflate the air springs.

4.6.1.2 Remove the bolts connecting the guide spring bracket, guide spring, and shock absorber. Then remove the U-bolts and accessories connecting the guide spring to the axle, and take out the guide spring.

4.6.1.3 Use a press to remove the old rubber bushings. Clean the eye holes, check for damage or cracks on the spring. Do not attempt to repair cracked springs—replace with a new one.

4.6.2 Installing New Bushings

4.6.2.1 Use a press to install new rubber bushings into the spring eyes, ensuring symmetrical projection on both sides.

4.6.2.2 Reinstall the guide spring on the axle, connect it to the spring bracket with bolts, and reinstall the shock absorber. Tighten all bolts to the specified torque (see Appendix 1).

4.6.2.3 Supply air pressure of 0.6–0.8 MPa to restore normal ride height and remove the jack or stand. Check that there are no leaks and the air springs are properly inflated.

4.6.2.4 Verify that the vehicle runs smoothly, remains level, and tracks straight without deviation.