Rear air suspension jacked up, won't release air

[TowGMC]

I finally figured out what's wrong with my Denali. I've been thinking that the back end was too high and was trying to figure out how to get it lower. But the problem seems to be the rear self leveling suspension.

I threw about 500 lbs of pea gravel bags in the back yesterday, and the rear drooped, did not pump up. So while the bags were in there, I hooked up the race car trailer- about 600 lb tongue weight for a total of close to 1100 lbs on the back- and it dropped down onto the bump stops. Did NOT pump up.

So it appears that the reason my tail end is high under normal driving is that at some point the rear pumped up when I'd had the trailer hooked up, but never released the air later. I pulled the two fuses that I was able to ID that are for the air suspension, but both were OK. No warning code (CEL)displayed on the dash.

Before I take it back to the dealer, which is a royal pain distance-wise, am I missing anything I should be checking? Or can anyone tell me if there's a way to bleed air off the system without having to disconnect the pump? At 40,000 miles I'm out of the bumper to bumper part of the warranty and really don't want to drop big $$$ into repairs so soon.

 

[KMeloney]

Just giving you a bump here. I don't know the answer, but I'd like to know if there's a manual way to bleed the shocks, too.

 

[kses123]

Just unhook the hose from on of the air-shocks. It is pretty easy. There is a little metal clip that holds it on. Just pry it apart where it overlaps. You only have pry it enough to be able to slide the air hose connector off. There is a little groove that the clips rests in on the shock, so you just get it over that and then it'll go PSSHHHHHHH with the air coming out.

 

[OHSIXX]

+1 on what Keith said......

When is the last time you heard your compressor kick in??

 

[stevek]

word of warning, you won't want to be under the car or have your hands in that area unless the thing is on jacks/a lift

 

[kses123]

You don't necessarily need it on jacks. It only drops down about an inch when you unhook the air shock. The air shock is not the only thing holding up the rear. The spring/shock do most of the work back there. The air bags on the shocks are just a supplement.

Now, if you were removing the entire shock that would be a different story...

 

[stevek]

You don't necessarily need it on jacks. It only drops down about an inch when you unhook the air shock. The air shock is not the only thing holding up the rear. The spring/shock do most of the work back there. The air bags on the shocks are just a supplement.

Now, if you were removing the entire shock that would be a different story...

You never know. Better safe than sorry. Sure you stupidly work on a car on a jack, but I'd rather use a stand. Just saying.

 

[TowGMC]

Like several have suggested (thanks!), I did release the air from the shocks. Can actually get to the fittings from the wheelwell without having to get under the truck. Interestingly, one side has the plastic clip but the other has a metal clip that's entirely different.

Released the air. Rear dropped a inch. Turned on the key and it pumped right back to where it was.

So I hooked up my trailer, the rear sagged 3.5". Turned on the key and it only lilfted the rear 2". So it was still low in the back. Hooked up the Reese spring bars (part of the hitch/ sway control system) that I use to keep everything level when loaded, got the truck and trailer heights where they should be, turned on the key and it let air out of the rear shocks! Never did that before. Unhooked everything, and the system released more air, dropped down but still ass high.

Based on all this, I know the compressor is working, and the two level links and rheostats are working somewhat. So I'm thinking something is out of calibration. Every time I pull the lines off the shocks and release the air, they pump right back up when reconnected. I assume the airbags need to have some air in them at all times to keep their shape, but how much is my big quandry now.

 

[kses123]

Try letting the air out of the shocks. Then disconnect the battery, both terminals. Touch them together and let it sit unhooked for a little bit. 30 mins maybe? Then hook the battery back up. This should at least refresh some of the computers/sensors.

Letting the air out of the shocks has nothing to do with this, but at least you could start from empty then let it fill to what it needs to.

Yes, there is always some air in the bags too.

 

[AndrewS4365]

What was the outcome of this? Having the same issue.