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Installation and Use of Single Axle Lifting Type Semi Trailer Air Suspension(Part 3)

Views: 0     Author: Wondee Autoparts     Publish Time: 2022-01-25      Origin: Wondee Autoparts

Installation and Use of Single Axle Lifting Type Semi Trailer Air Suspension

-Maintenance Cycle and Troubleshooting of Main Parts(Part 3)

1. Air suspension maintenance cycle

As shown in Table 1 below.

Normal use

Maintenance   cycle

Inspection items

Inspection   contents

Regular inspection

After the first load travel

Every three months or 25000 km

Every six months or 50000 km


Visual inspection for damage and wear

Air bags

After driving on asphalt road in summer, driving on muddy road after rain and other harsh environments, check and keep the air bag and its piston (base) clean.

Check whether the airbag surface is damaged (cracked, worn, wrinkled, surface foreign matter intrusion, etc.)

Check the fastening of airbag fastening bolts

Pneumatic circuit

Check and maintain the cleanliness and integrity of the air filter

Check the air tightness of valve body and pipeline connection, whether the installation is tight and whether there is damage

Shock absorbers

Check the tightness of the upper and lower pistons of the shock absorber

Check the tightness of the shock absorber and replace if there is any leakage


Check the tightness of the nuts of the U-bolts. If loose, tighten the nuts alternately diagonally

Bolts of main beam and shock absorber

Check the locking condition of self-locking nuts of bolts of main beam and shock absorber


Slightly brake the semi-trailer to move forward and backward, or pry the main beam at the bushing with a pry bar. At   this time, the main beam shall not be loose. Otherwise, the main beam or shock absorber bushing has been damaged. Replace it.

Lifting device

Check the fastening condition of lifting airbag fastening bolts and nuts.

Air tanks

Check the working condition of the drain valve at the bottom of the air tank, and   replace it if it is blocked.

(Table 1. Maintenance table)


The road conditions and specific use conditions of vehicles in each country / region will be slightly different. The maintenance cycles in the above table are for reference only.

"●" means maintenance.

2. Troubleshoots of air suspensions

2.1 Troubleshoots of air bag assembly

As shown in Table 2 below.




The airbag cannot be inflated

Airbag damage and air leakage

Replace the airbag

Pneumatic circuit abnormal

Check and repair the pneumatic circuit system

Load Sensing valve damaged or improperly installed

Replace or Adjust the load sensing valve

Failure of the pressure protection valve and pressure limiting valve

Adjust or replace the valve

Airbag damage and base rupture

Gravel and other hard objects are drawn between the airbag and the base, causing friction

Replace the damaged parts, check and clean the airbag frequently

The airbag was pierced by a hard object

Replace the airbag

Improper suspension mounting height

Replace the damaged parts and adjust the suspension height to the   correct

Severely overloaded

Replace the damaged parts and load according to rated load

Improper installation of the suspension and chassis frame

Replace the damaged parts, adjust or reinstall the suspension

Friction between the tire or brake system components and the airbag

Replace the damaged parts, eliminate interference and reinstall

Friction between the brake chamber and airbag

Replace damaged parts and change the installation position of air chamber or clamp.

(Table 2. Troubleshoots of airbags)

2.2 Troubleshoots of shock absorbers

As shown in Table 3 below.




Shock absorber oil leakage

Long service time, failure, oil seal damage, broken at the welding position

Replace the shock absorber

Shock absorber deformation

It is impacted abnormally, interferes with other parts, exceeds the stroke and stretched excessively

Replace the shock absorber

At the maximum stroke, the piston is stuck and accidentally impacted during stretching

Replace the rubber block and baffle

The nut of the shock absorber falls off

The nut is not tightened to the specified torque

Tighten the nut to the specified torque

Abnormal noise of shock absorber

The internal parts of the shock absorber are damaged

Replace the shock absorber

(Table 3. Troubleshoots of shock absorber)

2.3 Troubleshoots of Load Sensing Valve

As shown in Table 4 below.




The load sensing valve cannot correctly control the air inlet and exhaust of the airbag

There is no compressed air in the pneumatic circuit, or the valve is blocked by dirt,  or the fastening screw of the regulating rod of the load sensing valve is loose, or the valve core of the load sensing valve is damaged

Check the air source, clean the load sensing valve, tighten the loose nut, or replace the load sensing valve

Air leakage of load sensing valve

The sealing ring of the valve element is damaged

Replace the load sensing valve

(Table 4. Troubleshoots of load sensing valve)

2.4Troubleshoots of Steel structural parts

As shown in Table 5 below.




Welding seam broken

long-term alternating load, there are   pores and slag inclusion in the welding seam.


Main beam damage

Severely overloaded

Replace the main beam and load according to rated load

Bad road conditions

Replace the main beam and drive slowly

Improper mounting height of suspension

Replace the main beam and adjust the mounting height of the suspension

Shock absorber damaged

Replace the main beam and shock absorber

Displacement of main beam

The main beam bolts or U-bolts are not fastened 

Adjust the main beam and tighten it according to the specified torque

Bad road conditions

Adjust the main beam, tighten it according to the specified torque and drive slowly

(Table 5. Troubleshoots of Steel structural parts)

2.5 Troubleshoots of pneumatic circuit

As shown in Table 6 below.




Air leakage in pneumatic circuit

Friction and damage between pneumatic circuit and moving parts

Check and reasonably arrange the pneumatic circuit and replace the damaged air hose

Pipe pneumatic circuit joints are damaged

Replace damaged joints

pneumatic circuit folding

Check and reasonably arrange the pneumatic circuit and replace the damaged air hose

Insufficient air pressure of airbag

Insufficient air   supply pressure 

Make the air supply pressure of the tractor reach not less 0.6MPa

The pressure protection valve is working abnormally

Check and replace the pressure protection valve

Load sense valve   not working

Check and adjust   load sensing valve

pneumatic circuit damage and air leakage

Find the air leakage and replace the damaged air hose

Slow response of level valve

Insufficient air supply pressure

Check the pressure protection valve and the air supply pressure of the tractor

The pneumatic circuit blocked or damaged

Check and repair the air circuit system

The pneumatic circuit was frozen

Unfreezing and draining air tanks

(Table 6. Troubleshoots of pneumatic circuit)

3. Vulnerable parts list of air suspension

All rubber parts and non-metallic gaskets in the air suspension system are classified as vulnerable parts, including:

1) Rubber block of shock absorber;

2) Rubber joint of load sensing valve adjusting rod;

3) Rubber bushing of air linker;

4) Wear resistant washer.

4. Tightening torque table for air suspension standard parts

As shown in Table 7 below.



Tightening torque(N·M)



Nut M8


Fastening load sensing valves


Nut M16×1.5


Installation of lower brackets of load-carrying airbags


Nut M20×1.5


Installation of shock absorbers


Nut M22×1.5


Fastening U-bolts and torsion beams


Nut M30×2


Bolt tightening of air linkers


Nut M12*1.75


Fastening airbags and brackets

(Table 7. Tightening torque table of air suspension standard parts)

Note: the above contents are for reference only, please follow the manufacturer's manual.

Compiled by  WONDEE Autoparts


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