You may have an air suspension system on your skoolie and wondered what it is. Air suspension systems are designed to raise or lower your vehicle depending on the terrain you’re driving through, which can help with stability in turns, bumps, and steep climbs. It also reduces wear and tear on your shocks since they don’t need to work as hard when you’re not hitting bumps all the time.
These systems do come at a cost though- they are typically more expensive than traditional shock absorbers found in cars today because of their complexity. This blog post will discuss everything there is to know about air suspensions and how to replace one.
What is an air suspension system?
An air suspension system is a system that utilizes compressed air to raise or lower your vehicle depending on the terrain you’re going through. This makes it easy for your shocks to handle the terrain and they don’t have to work as hard when you’re not hitting bumps all the time.
There are many benefits of an air suspension system, but there aren’t any drawbacks that usually come with them. Although an air suspension system is typically more expensive than a traditional shock absorber found in cars today, the benefits outweigh the costs.
How an Air Suspension System Works
Air suspension systems function by utilizing compressed air to either raise or lower one side of the vehicle while leaving the other side unaffected. They can control both bounce and downward travel, and generally offer more adjustment than coil springs. This is because their applications are not limited by things like weight distribution and tire pressure, where a coil spring system may need additional components to work properly. Air suspensions utilize a pump to provide the increased pressure while maintaining a constant volume.
Parts of an Air Suspension System
A typical air suspension system is composed of three major components. The first of these three components is the compressor, which uses the engine power to turn the pump that moves the air into the fluid lines. This then moves to an accumulator, which will store compressed air. Between this and a check valve, there will be a fluid line that connects the two components.
The second component is an air line, which goes from the compressor to both left and right valves on your vehicle’s frame. A check valve opens up when one of these valves closes, preventing any excess pressure from being transferred back to the compressor or any other part of your vehicle.
The third component is an air spring, which allows for lowering or raising your vehicle by transferring air pressure from one side to the other. A check valve prevents the redistribution of any excess pressure from being sent back to the compressor or any other part of your vehicle.
A fourth component is a leveling valve. A leveling valve measures the height of the suspension, then provides more or less air to adjust the height.
Benefits of an air suspension system
There are a few benefits and drawbacks associated with an air suspension system. One of the advantages of having a great suspension system is that it will provide a more comfortable ride on rough terrain.
Disadvantages of an air suspension system
A disadvantage, however, maybe that you’ll need expensive repairs if your compressor malfunctions.
How to Replace an Air Shock
Replacing an air shock can be difficult if you don’t know what you’re doing, but luckily this guide will show you how to do it.
Jack up frame
I’ve seen videos where someone started the bus, allowed the compressor to fill the air shocks and bring the bus up to normal height. Then he pulled the air hose from the airbag and folded it over on itself and taped it kinked to hold pressure in the system.
It worked in the video, but I worried about damaging the airline. So, to keep the bus frame at height, I started the bus, allowed the air shocks to inflate, then stacked cribbing and a bottle jack up enough to support the bus frame.
I’m not sure if this was totally necessary because the strut pulls up on the bottom bar keeping the distance between the two constant, but I felt better about supporting the frame.
Bleed Air to Relieve Pressure
My air bag was leaking so badly that when I turned off the bus the air pressure drained through the leak. But, if you don’t have a leak in your system (yet) you may want to relieve the air pressure in the system.
To do so, simply open the valves on the bottom of your air tank.
Disconnect Air Lines
With the frame supported and the air pressure drained, I disconnected the air lines from the fittings on the air shock.
Like most skoolie projects, this can be easier said than done. The fitting has a “shark-bite” like connection. To release the airline, you have to push in the collar on the fitting then pull the airline straight out. (If you pull it from an angle it won’t come out.)
Problem is, dirt and grime get into the space around the collar making it difficult to push in. So I sprayed PB-Blaster around the collar, then used a thin flathead screwdriver to clean out the collar. Once it was clean, I could push it in and pull out the airline.
Remove Bolts on Mounting Brackets
Because of the rust, I had to use a breaker bar to loosen the nuts on the mounting brackets. And, of course, crawling around under the bus makes it even more challenging.
There are two mounting brackets, a thick one on the inside of the bus frame and a thinner one on the outide. Since my air shock was so rusted on the top, I found it easier to remove by removing the entire bracket from the bus, then remove the bracket from the air spring.
I removed all the bolts, including the one on the bottom.
Removing the Air Spring
Then, using a pry bar, I pried the air spring up from the bottom, comressing it enough to free the bottom bolt from the mounting bar.
Removing the Mounting Bracket
The rust rendered the air shock, the bracket, nut, and the washers all one piece. I needed to separate them!
I sprayed the bolt liberally with PB-Blaster, then clamped the air shock to my deck stairs. With a breaker bar, I loosened the nut. The washers were also rusted on pretty well, so I used a pipe wrench to loosen the lock washer.
With all that loosened up, I whacked the bracket with a hammer until it came off!
Removing the Air Fitting
Using a wrench, I removed the air fitting from the old air spring.
Attach Inside Mounting Bracket to Air Spring
In retrospect, I should have sanded down the mounting bracket and painted it. But I was pressed for time, so I didn’t. Instead, I sprayed it with oil then attached (loosely) it to the new air spring. (I figured keeping the nut loose would make it more “flexible” in getting it back into place.).
Installing the New Air Spring
The new air spring had a new outside mounting bracket attached. To make it easier to wrestle into place, I removed it.
Then, I squeezed it together to compress it. I tried to put the plastic cap that it came with it covering the air fitting port to keep debris from falling into the air spring, but it wouldn’t fit with the nut and bracket on it. So I did the best I could with duct tape.
Next, I wiggled it into place under the bus and once again used a pry bar to lift the bottom bolt up and then into the hold of the mounting bar.
I installed and tightened the bolts securing the inside mounting bracket to the frame.
With those bolts installed, I tightened the nut on the air port, holding the bracket to the air spring.
Next, I put the outside mounting bracket onto the air spring, but just barely put on the bolt. This allowed me more “wiggle room” to insert the bolts into the frame. Once I had those bolts secured, I tightened the bolt that held the outside mounting bracket to the air spring.
Attaching the Air Fitting to the New Air Spring
I put permatax thread compound on the air fitting threads, then screwed the fitting into the air port, then inserted the air line into the fitting.
Checking the System
With everything bolted into place and the airline attached, I started up the bus, waited for the air pressure to build, then crawled back under the bus to listen for air leaks.
I watched the air bags inflate…and heard no leaks!
Conclusion
Crawling around under the bus banging my head on steel parts wasn’t the most fun job I’ve ever done. But I was able to do it.
Now I have new non-leaking air springs!