Mechanics

Suspension Air Compressor

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Suspension Air Compressor
Suspension Air Compressor

Vehicles equipped with self-leveling suspensions, or ride-height adjustable suspensions are equipped with an on-board air compressor. There are even aftermarket overload springs and air suspension bags that utilize an on-board compressor system. In this article we will explain what the compressor does and some of the signs that yours may be going out.

Self-leveling suspensions have been around for many years, from luxury cars to SUV’s the theory remains the same; when excessive load changes the ride height of a vehicle, air bags coupled with height sensors and a compressor compensate for the load and bring the vehicle back to level, restoring ride and control. Some vehicles, such as Land Rovers have suspension height selectors for different situations; entry into the vehicle (Lower), off-road situations (higher) and highway use (Middle), all of these use an air compressor to achieve their goal.

At the heart of these systems is the compressor. All air compressors work on the same principle; take outside air (already at 14.7 psi), and by means of veins, pistons or screws compress the air into a smaller area, thus creating higher pressure or psi (pounds per square inch). Some systems use a storage tank that the compressor fills to keep things working, others have pressure switches in the bags that tell the compressor when to stop filling them, coupled with height sensor information. Air compressors in vehicles tend to be fairly small, but powerful units, usually with a maximum working pressure of around 150 psi. Their compact size and high working pressures create a lot of heat, which can cause compressor failure if the unit runs for too long of a time. This is common in a vehicle where there is a leak in the suspension and the compressor has to run continuously or many times in a short period of time to keep the vehicle level.

Some air compressors have their own internal check valves to keep the system full; others rely on valves at the air bags, storage tanks or at the valve block (Land Rover). These valves are also a common cause of compressor failure due to excessive run time and or overheating. When replacing the air compressor in your vehicle there are many choices. There is a large aftermarket parts source for these vehicles as compressor failure is fairly common. Always use an OEM (Original Equipment Manufacturer) part or the equivalent. A cheaper compressor won’t last as long and may cause suspension failure, which can cause loss of control of the vehicle.

Replacing the compressor in your vehicle isn’t a real complex procedure, but as always proper safety attire should be worn, and it is best to refer to a shop manual for your vehicle to see if there are any special relearn procedures or precautions that should be taken to avoid injury and to assure the repair is done correctly. Usually you can do the repair with the basic tools; socket set, screwdrivers, wrenches. When replacing the compressor, you should also replace any sealing o’rings that you have disturbed; this may avoid a leak in the future that could damage your new compressor.

If further technical assistance is needed, ask our team of certified car repair technicians.

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AUTHOR


Written by
Co-Founder and CEO of 2CarPros.com
35 years in the automotive repair field, ASE Master Technician, Advanced Electrical and Mechanical Theory.


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Article first published (Updated 2013-11-30)