Kenworth Air Suspension Issues Explained

In this brief article we are going to discuss the different Kenworth Air Suspension problems, what the causes are, and Troubleshooting Tips.

What are the most common Kenworth Air suspension issues? 

The most common Kenworth Air suspension issues are:

  • Air Bag Leakage
  • Rough Ride Issue
  • Suspension not lifting
  • Torque Rod bush failure
  • Sway Bar Bush Failure

Kenworth Air Suspension

Depending on the configuration and application, different Kenworth trucks get fitted with different types of air suspensions.

Some of the different Kenworth air suspensions are:

  • Hendrickson – PRIMAAX EX Air single axle 2 air bag Suspension System on the Kenworth T270 and T370
  • The AirGlide AG 130 Single Axle 4 Air Bag system as an optional package on the W990
  • The AirGlide AG 400 Tandem axle 4 Air Bag system seen on the T680

Kenworth 8 Bag Suspension

Kenworth 8 bag Air suspension is a Tandem Axle suspension that features 4 Air bags per axle; 2 Air bags ahead of and 2 Air bags behind each axle.

The different versions of 8-bag air suspension found on Kenworths were the AirGlide 100, 200 and 400 models.

Air Bag Leakage

  • Air bag leakage, in more cases, is a sudden Blow-out event because of the very nature of the duty cycle that the trucks are put through
  • The advantage with the 8-Bag system is that, even if one air bag blows out, it would be possible to level the chassis to some extent by lowering it and supporting at the remaining 3 corners.

Rough Ride Issue

  • Several of the Kenworth 8 bag suspensions reported a rough ride issue especially when they had the Airglide 100 suspension
  • The issue seems to be related to the way that the Air suspension Ride height is set up
  • The Air Bags have internal bump stops that are relatively huge
  • The level control valve needs to be calibrated in such a way that the Normal Ride Height of the truck is high enough with sufficient travel to avoid contacting the bump stops
  • The issue is best sorted out by an experienced Kenworth mechanical expert

Suspension not Lifting

  • This issue is mostly seen on the AirGlide 400 Kenworth W900 L Model
  • After lowering, Hitching and loading the rear suspension fails to lift
  • The issue is related to the rear suspension level control sensor. If the sensor is either broken or not properly calibrated, the air supply valves to the rear air bags do not get opened
  • One more possibility is if there is a leak in one of the air bags. In case of an air bag leakage, the compressor is unable to compensate for the loss of pressure

Torque Rod Bush Failure

  • In the AirGlide 100 8 Bag air suspension, there are a total of 8 Torque Rods (4 above and 4 Below) that connect the chassis to the 2 drive axles via rubber bushings
  • The torque rod bushes wear out and tear over time.
  • Since there is no Anti-roll bar for each axle, the torque rod bushings resist the axle roll motion.
  • Torque Rod Bush wear out, therefore leads to problems in Handling behavior of the truck and noisy suspension on rough surfaces
  • The bushes, which are typically of rubber, are of a serviceable design and can be replaced with aftermarket poly bushings which offer orders of magnitude improvement in service life.

Sway Bar Bush Failure

  • In the AirGlide 100 suspension, there are a total of 2 Sway Bars (1 on each axle) that connect to the chassis and to the 2 drive axles via rubber bushings
  • The Sway Bar bushes wear out and tear over time.
  • The Sway bar for each axle resists the axle roll motion through the bushings.
  • Sway Bar Bush wear out, therefore leads to problems in Handling behavior of the truck and noisy suspension on rough surfaces
  • The bushes, which are typically of rubber, are of a serviceable design and can be replaced with aftermarket poly bushings which offer orders of magnitude improvement in service life.

Conclusion

In this brief article we have discussed the different  Kenworth Air Suspension problems, what the causes are, and Troubleshooting Tips.

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