Mechanics

REAR AIR BAG SUSPENSION REGULARLY GOES FLAT

2004 GMC Envoy

Suspension problem
2004 GMC Envoy 6 cyl Two Wheel Drive Automatic 72,565 miles

While I don’t think it’s relevant, I noted that one of your other members reported that their air bag problem started just after the battery went dead. In my case it was 3 days after replacing the original battery.
The problem is that, with increasing frequency, the air bags go flat over night after parking the Envoy at home. If it makes any difference, it’s an XUV model. The dealer has checked the fittings for leaks and found nothing. In fact, for the two days it sat at the dealership, the rear height changed only slightly up and down due to temperature changes. When I brought it home last Friday, I left the key on and stood on the rear bumper to force the leveling system to operate. Once I got off, it settled back to what seems to be the normal ride height. It stayed fine until Saturday evening when I drove it around town on an errand. I parked it this time and just turned key off. The next morning, it was down over two and a half inches on each side. Any ideas on what to look for? I know that it has 3 solenoid valves. One for each side, and one to relieve pressure when the pump starts. Any chance one of the bag valves is hanging partially open and deflating the system?
Avatar
BobLR
September 15, 2008.



Sounds like that is exactly what is happening. For it to sink the same amount on both sides it might be the motor bleed off valve that is letting it out, it would be quite a coincidince for the left and right valves to stick at the same times

Tiny
Jack42
Sep 16, 2008.
Seems like both left and right valves would have to be sticking for the motor bleed off valve to cause the problem. If I understand the system, the pump output goes to a " header" from which pressurized air can go to the left or right air bag if the left or right solenoid is open, or to the inflation station inside the back of the vehicle. The inflation station has what looks like a regular tire schrader valve. The third solenoid valve briefly releases the pressure from the " header" so that the compressor isn't starting against a load. Once the compressor is running this third valve closes. My main point here is that, if I understand the system correctly, that the third solenoid (motor bleed off valve) is in parallel with the 2 solenoids controlling flow to the air bags. It does occur to me that I don't know where/how the system bleeds air from an air bag to lower a side after the load is removed from the vehicles. Any other thoughts?

Tiny
BobLR
Sep 16, 2008.
My software is very vague about how this system works. Does the inflate switch light ever blink? If so count the flashes, these are codes for the suspension system. I would figure that the left/right valve would open to allow air to be dumped, as to where it releases it, all Mitchell mentions is an exhaust valve that dumps pressure. There are a few TSB's (tech service bulletins) on diagnosis of the rear system. Check the main connector for loose condition or poor pin contact. Always support the vehicle when working with air bags

Tiny
Jack42
Sep 17, 2008.