Liquid Spring Suspension Issues Explained

In this brief article we are going to discuss the probable Liquid Spring Suspension problems, what the causes are, and Troubleshooting Tips.

What are the most Probable Liquid Spring suspension issues? 

The most “Probable” Liquid Spring suspension issues are:

  • Hydraulic Fluid Leakage
  • Strut Failure
  • Power Unit Failure

Liquid Spring Suspension

Liquid Spring is a manufacturer of the Liquid Spring Active Suspension Upgrade Kit  that is meant for Recreational vehicles (RV’s or MotorHomes) also called ‘Class A or C’.

The Liquid Spring System in Polaris is an intelligent Active 

suspension system that dynamically and continuously changes Spring rate as well as damper settings according to sensor inputs. The Liquid Spring system adjusts the shock absorber valves electronically to maximize ride comfort and all at the same time stability. LiquidSpring is a modular suspension system with its major ingredient as a shock-absorbing liquid, which also does the job of a spring.

Stiffness is controlled by means of a Rate valve which connects the Strut to the liquid reservoir. Low stiffness is when the rate valve is opened and liquid is allowed to  flow between the strut and the volume reservoir. High stiffness happens when the Rate valve is closed, preventing the Liquid from flowing from the strut back into the reservoir.

The Strut Module is very similar to a hydraulic damper, but with the difference that it is not one chamber, but 2 chambers in series. The Lower ‘Rod’ side chamber is expandable and liquid volume varies in  order to adjust height. The pressure in both the chambers is maintained equal. Damping is achieved by Valves in the piston in the upper chamber, just like a normal hydraulic damper.

The suspension set up provided by Liquid Spring is of a modular construction of basically a 5-Link non-torque reactive rear axle. Hence, proper driveline angles are maintained at all ride heights, in order to minimize driveline vibrations.

The 2ND FLUID VOLUME or Reservoir is a pressurized hydraulic chamber mounted to the chassis. The reservoir is connected to the strut via conventional hydraulic lines and connector fittings. The reservoir is responsible for controlling the spring rate change via the rate valve. The Reservoir is crucial in maintaining the performance of the LiquidSpring Smart Suspension System.

The Power Unit sends power as well as communicates with the pump, motor, manifolds, control valves, filters, low-pressure reservoir and the ECU which controls all the functions.

At the Driver’s seat are 2 switches that control the suspension ride height in steps, as well as ride mode to control Damping and Stiffness.

Relevance of Liquid Spring Suspension

  • The RV market is categorized into 
    • Class A, which is the largest size upto 45 feet
    • Class C, or mid-size with sizes ranging 20 – 31 feet
    • Class B, or small-size with sizes ranging 17 – 19 feet
  • Because of the premium  price tag of $20,000 for a front & rear suspension conversion, Liquid Spring’s target customer is the potential Large-size RV, or Class A RV buyer
  • Class A Rv’s are generally Diesel Pushers(engine at the rear) with high-powered turbocharged Diesel Engines
  • Class-A RV’s are also almost always with an Air Suspension as standard
  • With all the standard features, a Class-A RV would attract a huge price tag
  • A Gasoline engined RV in Class-A size would cost far lesser since Gasoline engines are cheaper priced and mostly do not come with Air suspension as standard
  • The Gasoline engined RV buyer could invest in fitting a Liquid Spring suspension with the money he would save by not opting for the Diesel
  • Liquid spring suspension would provide all the benefits of an air suspension plus an added advantage of Handling/Roll characteristics improvements

Potential problems with Liquid Spring Suspension

  • There is not much data available as to what actual issues the Liquid Spring RV owners have faced
  • The reason for this could be that there are very Liquid Spring fitted RV’s around, owing to the pricetag
  • Also, the Liquid Spring suspension has been around for a comparatively shorter period of a maximum of 4 years in the market

Judging from the component layout of the Liquid Spring set up, the following problems could potentially arise:

Hydraulic Fluid leakage

  • The Liquid Spring needs to operate at a moderate pressure
  • Hence, all the hydraulic lines and connector fittings at the Reservoir, and the Struts could be potential weak spots for leakages
  • The actual frequency of leakage occurrence with RV’s would largely depend on the quality of the Hydraulic lines and fittings and the robustness of the assembly process.
  • Also relevant would be any kind of Pre-delivery Testing that LiquidSpring has in place

Strut Failure

  • Though the Hydraulic Strut is different from any conventional hydraulic damper, it is still conceptually similar.
  • The closest resembling product already seen in the market would be the rather complex and advanced LandCruiser 200 series Active Height Control (AHC) and Active Variable Suspension (AVS) system that used a hydraulic pump, Gas accumulators and shock actuators to actively control ride height, Spring rate as well as Damping.
  • Another similar example would be the Citroen Hydropneumatic System.
  • That being said, the Strut’s durability lies in its ability to seal.
  • The potential weakest points, likely to leak, would be the Top Rod seal and the lower expandable reservoir of the strut

Power Unit Failure

  • As seen with other advanced electronic automotive suspension control systems, the Power Unit is a potential failure point
  • Electrical connectivity issues, have been observed in almost every car model that had Electronic Suspension Control
  • Being a complex system, the ECU within the Power Unit could fail in countless ways

Conclusion

In this brief article we have discussed the Probable Liquid Spring Suspension problems, what the causes are, and Troubleshooting Tips.

For any queries or Comments, please feel free to ask.

References

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