1999 Cadillac Deville • V8 FWD Automatic • 122,000 miles

My 1999 Deville is bottoming out when I hit bad bumps, go over speed bumps, or up and down driveways. Forget about it if people are in my back seat! Wow! When traveling at reasonable speeds, my car also seems to be bouncing from left to right.

My mechanic said my air bags in the rear are shot. The compressor keeps running because the air bags don't fill. He is afraid to repair the rear air brakes thinking that the compressor will go soon because of it constantly running and he says then I would have a major expense on my hands.

He suggests buying a conversion kit and installing standard shocks on my rear and doing away with air shocks. What do you think? Will any mechanic do this? Is there a particular kit(manufacturer) that you would recommend if you think this is a good idea. Thank you.
April 3, 2012.

What you need is coil springs. Shock absorbers don't hold the car up, springs do. The confusion comes from the use of "air shocks". Those are air springs built into the shock absorbers to assist the springs and are often used to make the ride height adjustable.

Some cars use air bag springs in place of coil springs. When an air spring or hose springs a leak, which is real common, repairs can get real expensive. Ford is most famous for this and replacement parts are often not even available after a few years. I test drove a car with air suspension, then bought an identical new '93 Dodge Dynasty with standard springs and factory air shocks for load-leveling, and the car rides just as smoothly as that one with air springs. If you install standard springs and high-quality standard shock absorbers, I suspect your ride quality will be just as smooth as it was originally. At issue is what will fit in place of the air springs. GM is known for using many different designs with parts that don't interchange. That's why you have to buy kits with the proper retrofit parts. I don't think you're going to find a "bad" kit. If you can find one made by a well-known company such as Moog, Federal Mogul, or Rancho, you'll have a better chance of it fitting and working properly.

We used to install a lot of Moog "Cargo Coils" on GM and Ford cars to get the ride height back to specs. They are a variable rate coil spring. Part of it is wound with the coils far apart for smooth ride quality, and part is wound with the coils stiffer and close together for load carrying capacity. We had lots of very happy customers. A pair of those springs costs about $150.00. I haven't bought shock absorbers for a real long time, but a good one, I suspect, will run between 20 and 40 bucks. Sears typically has five grades available with the lowest grade being equivalent to factory original.

I would suggest starting with new coil springs, then if a little more height is needed when you have many passengers, you can install a pair of air shocks. GM typically put their height sensor between the axle and frame, and that would not be affected by converting to these new parts, so your mechanic should be able to connect your current compressor to the new air shocks. That will maintain the automatic adjusting feature. Otherwise it is customary to just mount an air fitting in the trunk or under the rear bumper. Then you have to visit a gas station to pump them up when necessary.

Apr 3, 2012.
Remove the linkage to the axle and push up on it. Key on an in rev. Start spraying the shocks and lines down with dish soap in a bottle. Youll find the leak.

Apr 4, 2012.