Hummer Forums - Enthusiast Forum for Hummer Owners - Should rear air suspension ever deflate on its own?

I figure I'd share my experience this week with my '03 H2 air suspension. Mine has only 25k miles on it and is dead show room stock right down to the original tires.

Im in Maine and a week ago I was out during a snow storm to take my mother to the grocery store. I brought her inside and came out to find the H2 on the ground. DIC displayed the "Service Air Suspension". Prior to that the truck never sagged ever no matter how long it set in the garage. Note with only 25k miles it sits for long periods. So I drove directly to my brother-in-law's shop and put it up on the lift. When we raised it the driver air spring was completely collapsed and came free from the axle mount. My conclusion was that the air spring had failed and immediately ordered a new set of air springs from newgmparts.com. Pleased that they were only about $130 each. Replacing these was a real surprise, taking less time and effort than changing the oil. Unfortunately when I set it back down and start the truck I got nothing. No compressor and still the Service Air Suspension message. I was very afraid that I had cooked the old single cylinder compressor which is unique to '03 and '04 before they upgraded to a dual cylinder. There was no power at all to the master relay which is under the brake master cylinder in the engine compartment, and no power to the compressor assembly.

I borrowed my brother-in-law's Snap-on scanner. It pulled codes for compressor overheat and also failed driver (left) suspension height sensor. I disconnected the trailing arm rod from the sensor in the rear wheel well and observer the resistance on the scanner as I moved it up and down. It didnt change the resistance at all. I did the same test on the passenger (right) sensor and could observe direct effect of moving the sensor arm. So I ordered a new Dorman brand sensor on Amazon for $120. With regular shipping to the end of the dirt road in Maine I still got it next day. Took 15 minutes to install. When I started the truck it immediately started the compressor and lifted to normal height. The driver side is 1/8 inch higher than the passenger and this can be easily calibrated with the scan tool if Im feeling obsessive enough about that small difference.

So point of all this is that if your H2 suddenly drops without prior sagging then it very well may be one of the ride height sensors. I think that when I picked up my mother at her home I may have damaged the vulnerable sensor when I climbed the truck over a snowbank at the end of her driveway. Snow and ice was flying everywhere. It was fun!

On the other hand, if the truck is sagging after sitting for a while then it's likely the air springs. My opinion on the air lines is that they are very tough and very unlikely that they would fail unless damaged from some impact. Considering the relatively low price of air springs and sensors it doesnt make any sense to ignore a leak or problem and make your expensive compressor work hard.

Its very worth while to find someone with a full function scan tool to narrow the possibilities. Still, if you cannot get use of a scanner, you can buy a lot of easily installable parts for probably less than the cost of just a few dealer labor hours.

A couple of things to share about changing the air springs.... the air line fittings on top of the air springs get corroded and are a little difficult. I sprayed them with penetrant to loosen them a bit then you just push down on the metal fitting and the line will release. If it wont release you could carefully cut it off close to the air spring; nice and square. The new OEM Firestone sourced air spring seem to have an improved fitting and seated easily.

Also, even though only my driver air spring had collapsed, I did decid to replace both bags. As the passenger bag was still pressurized I had to release the air pressure. I punctured it several times deeply with a sharp all. This did nothing. Contrary to most folk's comments, those air springs are tough. I then cut into it with a box cutter and was shocked by the bag bursting open like a gun shot. This was fine as I had the truck lifted on stands and was reaching into the wheel well over the tire to cut it so was just a loud surprise. Just have the truck lifted and secured, and keep your face away.

While I feel a little bad about spending nearly $300 to replace what were still perfectly good air springs at least can have a few years peace of mind that they shouldn’t be any trouble when deep in the northern woods or pulling our camper. Since the originals lasted 12 years in rather tough Maine climate Im actually pretty impressed. Overall the H2 has proven very durable and serviceable. Im certain mine will be running around Maine for another 10 or 12 years.

Hope this is helpful. Good luck everyone.