Rear Air Suspension troubleshoot help needed.

[KeithP]

Hello!. My (2009) Rear air suspension bags are not inflating and they are bottomed out. Compressor kicks on and off as expected when the rear end is lifted and lowered (with a floorjack), so the height sensors are probably fine as well as the compressor motor. One observation, when the compressor is running, air is leaking out from the airline/port directly at the compressor/dryer and the rear bags will not inflate. I pulled the airline out of the compressor and tried blowing compressed air directly into the airline to inflate the bags, but the lines and bags do not seem to be accepting the force air, the bags won't inflate.... almost as if something is clogged in the airline somewhere, which could be causing back pressure at the compressor and hence why air is being forced out at the port on the compressor.... but that seems practically impossible (to have a 'blocked' airline) - Oh, I also traced the airline all the way from the compressor back to each bag and could not find evidence of a pinched line. I didn't put a lot of air pressure on the air line because I wasn't sure if there was a solenoid/valve at the bags that are controlled by the height sensors or PCM to close off air to the bags and if so, possibly damage those by forcing too high of pressure while they are closed.... no idea how the system operates with respect to the solenoids at the bags.

I'd like to confirm if there's a leak in one of the bags, but without being able to force air into them, I'm not sure... and I'm not thrilled about the idea of pulling them off just inspect that. You can't really see the bags because they have the metal shroud around them. Also, I assume if 1 bag is bad, they both go down (is this true?) since they are tied in to the same airline feed.

One other thought is maybe it's the compressor assembly, even though the motor works, is it possible that this is just simply a broken or bad seal at right at the airline port at the compressor? Also, I think there is a vent solenoid built into the compressor assembly as well, maybe that vent solenoid is bad and that's the issue? I just hate to replace a perfectly good compressor assembly only to find out it could be an issue elsewhere.

Anyway, anyone ever have this kind of issue with their air suspension or some other experience and can give advice?

 

[MikeA]

You should be able to disconnect air line from air pump in vehicle, using a blow gun with a rubber tip, shoot air into the line to check for leaks.

My 1998 rear bags went down, i removed the air line from pump, shot air in the line with rubber tip blow gun, with ignition key to run position to activate air valves, bags leaked air.

Helps to have someone there to listen for the leak while shooting in air

If one bag is bad, best to replace both rears, considering if one fails the other one is close to if not already to leak

 

[KeithP]

Thanks Mike, I tried it this morning, pulled the air line out, turned ignition to run/start, compressor kicked on right away and I pumped air directly into the line using my home compressor set at about 90psi. I had a helper in the back listening for air leak and watching for any lift on the suspension. After about 30 seconds of forcing air into line, Right side, nothing at all, left side very negligible lift (maybe 1/4 inch). No audible air leaking from bags. I'm not sure how much psi to apply or how long the do it to safely conduct this test without damaging anything, so after 30 seconds with virtually no lift, I discontinued it. When I pulled the rubber tip away from the airline, the little bit of air that did go into the system came rushing back out, so apparently, the lines are holding pressure..... I'm stumped as to why the airbags will not inflate.

 

[MikeA]

Sounds like one or more of your rear fill solenoids not working.

To test , start with the rear fill solenoid on driver side of frame, on 1rst gens there on frame under driver door area, turn your key back to run position, put your hand on the solenoid, when your compressor kicks on, you should feel a click in solenoid, do the same for the rear fill solenoids on top of your rear air bags.

Might find it easier to remove spare tire to get more room to get to top of rear bag solenoids.

If you feel no clicking while hand on solenoids, next step,is to jump the solenoids with power , a portable jumper box works good, if you have one, or you can remove solenoids to jump with vehicle battery. Jumping power should cause solenoid to click, if not, faulty solenoid

The blow back of air, means the air never got to the rear bags, it stayed in the lines, usually meaning, solenoid(s), did not open to let air get to bags.

 

[MikeA]

curious, is the problem fixed?

 

[1997SCEBFEX]

not sure if the design is still the same, but this is very similar to the air union coupler not working. It's under the master cylinder on Gen 1's, not sure about yours though.

Best of luck & let us know what you find.

 

[KeithP]

Thanks for all the comments. I believe that I've discovered the issue. I did a closer exam of the compressor while it was running and there is a small leak at the union between the dryer and compressor. Can't believe I missed that!

I did confirm that the air solenoids were clicking (thanks for the tip MikeA). They both activated about 3 or 4 seconds after the pump turned on.

As for the test I originally did with my Air compressor, I can only deduce that it was not generating enough pressure. I later found on-line that some air suspension systems can operate at 125psi... my compressor was only capable of 80-90, so it was enough to push a little bit of air into the lines and bags, but not enough pressure to lift the body.
At this point, my plan is to replace the compressor assembly.

 

[gixer2000]

Thanks for all the comments. I believe that I've discovered the issue. I did a closer exam of the compressor while it was running and there is a small leak at the union between the dryer and compressor. Can't believe I missed that!

I did confirm that the air solenoids were clicking (thanks for the tip MikeA). They both activated about 3 or 4 seconds after the pump turned on.

As for the test I originally did with my Air compressor, I can only deduce that it was not generating enough pressure. I later found on-line that some air suspension systems can operate at 125psi... my compressor was only capable of 80-90, so it was enough to push a little bit of air into the lines and bags, but not enough pressure to lift the body.
At this point, my plan is to replace the compressor assembly.

Do you need to do the entire compressor or just the drier? Pretty sure they come apart and the entire compressor is pretty expensive

 

[MikeA]

Do you have the leak where the dryer connects to compressor, check o-ring

 

[MikeA]

Is this problem solved?