Another air ride thread

[Decado]

Sorry for the creation of yet another air-ride suspension thread but I searched through quite a number of them and didn't see my situation.

I bought my Envoy about a year ago and the dealership I purchased from installed new (at least I believe they were new) airbags due to the rear end sinking down immediately after the truck being shut off. They would inflate up right away upon starting, but clearly could not hold air. After they replaced the airbags, the system held air and I purchased the truck.

Fast forward to now and I have noticed the rear end of the truck is lower than it once was. I have noticed this over the past couple months but have not had time to really look into the issue and the ride has still been smooth, so it's more of trying to fix how it looks and before more problems are created. As of this morning, the left rear side is at 30 3/4" measured from the ground to the wheel-well, and the right rear side is 31 1/4". A couple days ago both sides were about a quarter to half inch higher, and all 4 tires are inflated to spec. I never really measured or paid close attention to the height before I noticed this, but it looks to be sitting lower than it used to. When I start the truck I can hear the compressor kick on and run for about a minute and then turn off. When it's running the height does not seem to go up or down at all. I have not noticed the compressor kick on any time other than when the truck is started, but it runs after every single start. The only other detail that I think may help is that back in April I had 4 new tires installed and I don't know if it's possible that the shop who put them on inadvertently adjusted a sensor or line for the suspension.

Any help for a next step of diagnosing this problem would be appreciated. Like most, I don't want to replace anything I don't need to and I don't want to pay for a shop to spend hours hunting down the problem if I am able to troubleshoot it with the help of the community. I'm not afraid to get my hands dirty but I am not sure what to look for next.

Also, before converting to coil springs is mentioned, I really like the ride of the air suspension system so I would prefer to keep it; a conversion might be an option depending on what the problem is and how much it will cost to fix the air system, but I want to figure that out first.

 

[Decado]

Some pictures, took the first 2 yesterday to show the current ride height.

This one is from 3 months ago. It's not the best picture but you can clearly see that the rear ride height is higher than it is now.

All of these pictures are with no significant weight in the vehicle.

 

[The_Roadie]

The sensors are easily adjustable. Just go look behind the tire, loosen the obvious mounting screw, rotate the sensor a tiny amount, then ride around and check the height after it's been exercised for a while. You can get 2-3 adjustments in a day using this tactic. Just remember it's not going to show instant results - the systems has to be exercised to become stable at a new ride height.

Your tire change place probably jostled them.

 

[Steevo]

That is all easily adjustable with the sensors in the wheelwell on each site. Decide what height you want and you unscrew and rotate the sensor, there is a lever that senses the height.

I did it, no big deal at all.

Haha. Roadie said the same thing. Great minds think alike.

FWIW I like the air ride, I would never go to coil springs like some talked about doing on those vehicles. This is perfect.

 

[Decado]

Thanks guys.

Do I need to take the tire off to adjust the sensors?

 

[The_Roadie]

I don't have them, so I can't tell for sure. Recommend you just go look at yours.

 

[Decado]

I'll take a look after work, just trying to plan my time while sitting at my desk.

From some pictures I found it looks like you can access the adjustment with the wheels on, with the use of a long extension 10mm socket.

 

[Steevo]

I'll take a look after work, just trying to plan my time while sitting at my desk.

From some pictures I found it looks like you can access the adjustment with the wheels on, with the use of a long extension 10mm socket.

That's exactly right, I think a 10mm socket on a long 1/4" extension, it was no problem. Very easy.

 

[Decado]

Update: I could reach the 10MM bolts for the sensors through the wheels with the use of a long socket extension, but it was difficult to adjust them so I pulled the wheels off to allow me a better view of what I was doing. I adjusted the sensors several times one direction and then back the other way, each time allowing a couple days and plenty of drive time to allow for the system to be exercised. Throughout this entire process I have not noticed any difference in ride height, higher or lower, but the height is still obviously lower than it should be.

While I had the wheels off this last time I put soapy water on the airbags and lines, just to check, and did not notice any bubbling so I do not believe the system is leaking. I continue to only hear the compressor run after starting the vehicle and although it runs, the suspension height does not go up at all. I drive about 45-60 minutes each way to work and have done multiple commutes with no radio, paying close attention to listen for the compressor and it does not run unless it's immediately after the vehicle starts.

Looking for help on the next thing to try or look for. Is my compressor on the way out? Is there a way to test it? Something else I can troubleshoot? Any advice is appreciated.

 

[jimmyjam]

have you tried using the tire inflator and seeing if that works? see if you can add a few psi to your tires or test with a basketball or something

maybe you can check the lines and see if there are any kinks. there is a hose for each bag coming out of the compressor.

 

[Decado]

The compressor does turn on when I hit the switch in the rear hatch area but I do not have a hose for that connection (didn't come with the vehicle when I bought it used) so I have not tried to see if it's actually moving air, but that's a very good thought. I just looked up that hose and see that an OEM replacement is $75+ and I would really rather not spend that kind of money just to test out the pump. I wonder if there is a generic one I could pick up at an autoparts store or somewhere like Walmart for a fraction of the price.

I inspected the lines this past weekend when I had the wheels off and soaped up the lines/bags; nothing looked kinked or out of place.

 

[Decado]

Some follow up for anyone curious or people who search this thread in the future: I tested the compressor with a hose and a basketball and the pressure was very low. I was due for a tire rotation and oil change so I decided to skip doing it myself this time and took it to a trusted shop who could also look at the suspension. They confirmed the issue is with the compressor, that it runs but doesn't put out pressure enough to do anything. They used another compressor to fill my air bags so the vehicle is riding better for now, as a short term fix until I figure out what to do.

If you want a good laugh, they wanted $995 to replace the compressor and $650 to to a coil spring conversion. This is a shop I know well and the manager told me not to have them do it since I could do this project myself. As much as I like the air ride system and want to keep the vehicle original in that aspect, the ~$450 price tag to do that job has me reconsidering since I think I can do the coil spring conversion for less than $200. For those who have done the conversion, I need to get the springs AND new shocks, correct?

 

[jrSS]

If your staying at the same height the oem bags were at keep the same shocks. All depends on mileage.

 

[jimmyjam]

well, shocks for springs vs airride are different part numbers, even aftermarket. probably different dampening.

http://www.2carpros.com/questions/gmc-envoy-2002-gmc-envoy-rear-air-spring-problems

the problem may be something stuck in the check valve in the compressor, or corrosion, etc.

http://parts.nalleygmc.com/products/COMPRESSOR-KIT-Air-Injection-Reactor-Pump-and-Multi---Function-Air-Compressor/2721052/15183676.html

the "kit" costs $25, may be worth looking into.