Greater Midwest Classics


By: Tim Anderson

We hear a lot of people talking about what new air bags they put in or should buy, but we don’t hear many talking about the air lines. We have a 1976 Palm Beach that from the day we bought it the air suspension would slowly leak down while sitting. Even after replacing the 40yr old airbags thinking that was the problem, the sagging continued. Driving along one afternoon an air line broke leaving us a bit lopsided. I thought maybe I routed the air lines different during the air bag install causing some stress, so I cut the line a bit shorter, installed a new brass ferrule and put it back together with an improved routing. A few days later the air line broke again. Turns out the 40+ year old air lines on our coach were pretty brittle, so it was time to replace them. I talked to Jim Bounds and he recommended using Parker 68P air fittings and DOT rated air tubing. 

The Parker 68P fittings (Poly-Tite) are a bit different compression fitting using an acetal copolymer (plastic) sleeve instead of a brass ferrule that reduces stress on the tubing. Fittings can be found at various sources. 

I ordered 30 feet each (73-75 GMC’s will need more as the pump and tank are in the front of the coach) of polyester blue, red, and yellow DOT-04 ¼” air brake tubing to match the original colors.  The tubing is about $0.5/ft and is available from many sources.

With my supplies in hand (and fuel tanks already dropped), I ran the new air lines and replaced every fitting in an afternoon. I believe this could be done without having the tanks dropped. The passenger side air lines route under the body to the driver side where all the air lines pass through a hole in the fender into the hall closet. To pull the new air lines in, I taped the new line to the old ones as I pulled them into the cabin. Repeat six times and all the air lines were in place.

I installed all the new 68P fittings, air lines, and a new Viair 91005 ½ gallon air tank all for about $200. I had previously installed a Viair compressor. I can now leave the GMC parked any amount of time without the air suspension sagging. Remember these rigs are 40+ years old. Everything plastic and rubber will break down and needs attention so as to not leave you stranded (or sagging).