Post by: Glennman

I have a series of green air lines fitted together below the driver's seat that were apparently once connected to an air dryer. On the wall next to them, where they are connected, there is a label showing the valve directions for on/off. However, there are no valves, only fittings, where it appears that someone took the dryer out and bypassed it by connecting the hoses together. What would that air dryer look like, and is it the kind that requires a filter assembly? I would like to install another one and get it back to OEM. Any thoughts? (My bus is a 2002 MCI D4500, 12.7 Detroit)

Post by: luvrbus

It will be an AD-9 unless it has been changed over to a Haldex. Pictures of this setup are all over the Internet. It will have a line in from the compressor, a line out to the tanks, and a ¼-inch control line from the compressor governor. They are simple and are easy to rebuild, unless the cover is rotten with rust. None have valves. You can buy an aftermarket dryer for $200. They work well; I have installed dozens with no problems. The Bendix will be around $600.

Post by: Utahclaimjumper

Haldex is the only way to go, and the rebuild kits are available and cheap. Dan, if you have a floor in that compartment, you will have to create a hole for the dryer to purge.

Post by: Glennman

The "compartment" that the lines are in is under the driver's seat, where there is an air tank and windshield washer fluid. The problem is that since the one that (apparently) was there is gone, I don't even know what it is supposed to look like. I wouldn't even know how to hook one up. I'll do some more research on the matter. There is a tour bus outfit down the road that will probably let me take a look at one of theirs. They still have a few D4500’s in their yard.

Post by: Glennman

While working on the front of the bus, replacing the shocks and a bearing seal, I finally found the air dryer. I had originally thought it was located under the driver’s seat where the washer fluid tank is because there is a three-way ball valve there with a diagram showing how to bypass the air dryer. The valve had been reinstalled somewhat haphazardly, making it look like the air dryer had once been mounted there. That led me to believe it had been removed at some point.