Troubleshooting rear air suspension

[Busterbrown]

The rear air bags have been problematic as of late. I originally thought the bags were leaking as my truck was sitting on the rear axle bumps after 12 hours. But only intermittently was this happening. Further investigating has lead me to believe the bags are okay and there maybe a failure elsewhere in the system. If the truck sits on level ground (or facing uphill on an incline) overnight, the ride height is normal the next day. If the truck is facing downhill on a decline, there is a compete loss of air in both bags. Anyone experience this before or have any ideas why I'm losing air out of both bags when the truck is facing downhill? I've been parking the truck with the front of the truck facing down the sloped driveway for months now assuming replacement bags needed for both sides. For the last week, I began experimenting and parking the truck the opposite direction (front facing uphill). Minimal if any loss of height in the morning. Stumped in Detroit.

 

[IllogicTC]

Perhaps a valve in the air compressor system is loose in some fashion, where gravity is more powerful than its spring or other closing mechanism.

 

[The_Roadie]

Concur. If it's not the bags or leaky lines, it's a check valve in the compressor assy. GM used to sell rebuild kits - not sure if that's current info.

 

[jrSS]

That's why most go with springs ( and helper bags if you tow ) oem system is junk.

 

[linneje]

It sounds like your check valve, as Roadie suggested. Because it is a problem related to the incline of the vehicle, one would suspect your sensors are trying to release air when parked downhill. This will be done by your check valve, and for some reason it is not closing when it should. If it is very quiet, I can actually hear the air escaping when I shut the vehicle off, and I can hear when it stops releasing air.

If it is really really cold (like -35 or 40) mine will sometimes freeze open when I shut the vehicle off and the air bags will completely deflate. But I have never had this problem in the summer.

 

[Wooluf1952]

IIRC, the valve rebuilding kit is about $35 from the dealer.

 

[Wooluf1952]

My google foo is getting better;

" Air-ride valve rebuilding kit+GMTNation.com" :

There is a check valve rebuilding kit available from the dealer (part #15183676, about $35) or possibly Rockauto. IIRC, it's for the check valve between the compressor and the air distribution block.

 

[northcreek]

Beyond the check valve there are other valves in the compressor which are not serviceable. With the age of your truck and being in the salt belt you no doubt have water in your compressor unit which is also the brains of the system. I would live with it and start saving for a new compressor, if you want to keep the air ride system.
Myself I have a new compressor in waiting because having an 07 I know that it's just a matter of time.
The check valve replacement is a cheap enough thing to try but, the success rate is minimal at best.
BTW I had my compressor out at about 60K (I'm also in the salt belt) and the rust was almost thru the case, I did a sand blast and paint job but could see the limited life of these things....Mike.