We hear a lot of people talking about what new air bags they put in or should buy, but I 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. After about 5yrs of ownership I finally replaced the 40yr old airbags thinking that was the problem, but the sagging continued. Driving 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 touch 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 are 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. He also mentioned that he typically can use the original air lines. Our GMC came from Kansas where it was parked outside most of the year. The sun and time had caused the air lines to become brittle. 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. I found all the fittings I needed (and a few extra) at shopcross.com.
I ordered 40 feet each (probably needed about 25 ft each for the 76, older GMC’s will need more) of polyester blue, red, and yellow DOT-04 ¼” air brake tubing from shop.hoseandfittings.com.
The fittings range in price averaging about $3 each and the tubing is about $0.5/ft shipped to your door. 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.
Older GMCs the air lines all run up in front of the driver’s tire. I also installed all new 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). Below is my air compressor and cabinet complete. Note, I have a air line quick connect installed next to the air tank. This allows for a quick air hose connect to fill tires, air bags, bike tires, footballs, etc. when needed.