My 98 Cadillac DeVille rear air suspension system works great UNTIL I load weighted luggage in trunk and passengers in back seat. I then drive around for 15 to 45 minutes and thats when the rear end of the car is bottomed out (wheel well is now down to the white stripe on tire). With car running I get out and do not hear the pump running to supply air to shocks. With no luggage or passengers the pump and car woks perfect. I have tried to fix problem by having dealership replace pump and leveling sensor ($1300+ so far). Dealership has checked air lines and air bags in shocks more than once and cannot detect any leaks. Any advice would be appreciated.

Rear Compartment Relay Center
In the left rear of the passenger compartment, behind the rear seat, on the electronics bay
Rear Compartment Fuse Block
In the left front of the rear compartment, on the electronics bay

if the front stays up the compressor is working
what you have indicates the ride levelling valves to the rear are not working properly
you can test the compressor by attaching a pressure gage to the outlet side

Something is broken or badly worn. There's a lot of potential causes so you'll need to get someone to look and make a proper diagnosis, but most commonly it will be due to worn or perished suspension bushings. If so, the suspension will need to be dismantled in order to fit new ones.

It can also be due to corrosion where the suspension mounts to the bodyshell or to the chassis, but this is all useless conjecture until you get someone to take a look ASAP. The fault won't fix itself, and will only get more expensive as it over-stresses other parts like springs, dampers, wheel bearings, tyres and it can result in unsafe handling and braking instability.

Had same problem with my Caddy POS . I took off left rear wheel and disconnected air line. Make sure you take fuse out of system in trunk behind back seat so that the problem doesn't occur again. Just let car ride on suspension. Should not be a problem as long as you don't overload trunk.

Do you hear your compressor running? It may be that it is getting tired and ready to burn out on you. I replaced the compressor twice on my Deville before I found that there were so many holes and nicks in the air bags and it was going to cost me almost $1500 to fix the whole system. I went online and found Strutmasters. I got a non air conversion kit for my car and love it. Saved me money and headache.

I have seen this before. They put car on lift which lets suspension drop. When they set it back down the Air ride leveling rods get stuck and think they need to stay full. Like what was already mentioned, check your levelers located next to your suspension air bags to see if they are stuck.

the leveling system does have an air pump - should be behind back tire under trunk on right side - the pump works from a leveling switch on the rear suspension

Its on passenger side under rear seat cushion. Get in back seat FACING rear seatback, grab under lip of bottom seat cushion, and pull straight up. Disconnect seat heater connector (if so equipped) on passenger side and remove seat bottom. Tada! There ya go! Oh... btw. Its a $150 battery due to the venting system designed into it to vent fumes through a tube to the outside world. Thanks Cadillac!!! :(

on my 1998 Deville its located in the trunk. the panel thats is butted up to the back of the rear seat. look for some black nuts around the top of rim of the trunk, they are about 1'' long, these have to be removed first... good luck.....

Mac.........

You may have either leaking shocks. follow the air line from the shock to the compressor.