Installing a air dryer.

johns4104s · January 20, 2010, 03:31:19 PM

Just were does the air dryer go between the air compressor and the line going to the first tank? Were is the best place to mount it? It would be easier to maintain at the rear. I would find it difficult to get at in front between the axle.

Thanks

john

bevans6 · January 20, 2010, 03:54:08 PM

The air dryer people suggest that there be about 6 to 8 feet of distance, which I take to be line length, between the compressor and the air dryer. My installation uses solid metallic line. The idea is to allow the hot air from the compressor time to cool, and hence more readily release it's moisture. I see no reason not to install it in the engine area, with a coil of line suitably installed, then up to the wet tank. You do want it to blow down on something that won't get all messy. Yes, it's a PITA to get at between the front axles, but otherwise a fine place for it to live.

Brian

johns4104s · January 20, 2010, 03:56:59 PM

Does the air dryer have a one way check valve on it to stop the air going back and forth to the compressor?

Thanks

John

DaveG · January 20, 2010, 04:01:42 PM

The line from the compressor to the dryer should be flexible and heat resistant, like the stainless braid covered teflon hose.

John316 · January 20, 2010, 04:49:12 PM

Quote from: DaveG on January 20, 2010, 04:01:42 PM
The line from the compressor to the dryer should be flexible and heat resistant, like the stainless braid covered teflon hose.

Interesting. Our line is made out of stiff copper. It is heat resistant, but not flexible.

God bless,

John

buswarrior · January 20, 2010, 04:56:33 PM

There needs to be the minimum mileage of piping between the compressor and the air drier in order to get the incoming air cool enough to not damage the desiccant. Driver trainers make up that other crap about temps and moisture. Bendix primarily cares about cooking the desiccant.

IIRC, anything above 150 degrees isn't good, the cooler the better.

As noted, and in many factory installs, there may be a coil of copper piping someplace back in the engine room/side compartments to provide enough mileage/surface area to get the temps down before entering a rear mounted air drier in a coach.

A worthy project to embark on!

happy coaching!
buswarrior

RichardEntrekin · January 20, 2010, 06:24:44 PM

Mine is tucked in the rear tag well on the opposite side of the coach from the compressor. That gives you a little piping run, and it mounts the dryer outside the heat of the engine bay. Only problem with that set up is you have to crib the coach to change the cartridge since you lose all air pressure when you remove the cartridge, and then of course the bus sits on the wheels keeping you from getting to the cartridge.

DaveG · January 20, 2010, 07:28:42 PM

Vibration is not copper tubing's friend, so when the compressor is mounted on the engine (rubber mounted) and the dryer is mounted on the chassis (rigid) there is nothing to absorb the vibration except the copper tube itself.

bevans6 · January 21, 2010, 06:07:49 AM

Quote from: johns4104s on January 20, 2010, 03:56:59 PM
Does the air dryer have a one way check valve on it to stop the air going back and forth to the compressor?

Thanks

John

John: the air dryer has two lines to it and one line from it. It has a main feed line to it from the compressor. On my MCI, this is actually a large line (I'm going to say 1" solid metallic, I have not actually looked at it to see what metal it is) from the ping tank, which is hard mounted on the front wall of the engine bay to the air dryer in the front axle bay, front wall. That line brings the air to the air dryer, and there is no check valve in that line. The second line to the air dryer is from the governor unloader port. that is a small diameter signal line that tells the air dryer when the compressor cut-out pressure is reached, and tells the air dryer purge valve to open. The air dryer purge valve remains open until the signal line tells it to close when the compressor cut in pressure is reached. so the air line from the compressor all the way to the air dryer is open when the compressor is unloaded. The final line is the line from the air dryer to the wet tank. This line has a check valve, at the air dryer end, so that air can pass into the wet tank but cannot come back out. This maintains pressure in the wet tank when the air dryer purges.

I hope this answers your question!

Brian

busshawg · January 21, 2010, 10:18:57 AM

I really don't mind the fact that my dryer is loacated by the steer axle. You can hear it working and it really isn't THAT bad to get at. I replaced mine with a AD9 last year and switched it to 12 Volt, just so if I do have problem on the road I don't get so many blank stares. Also with the dryer located up there you don't have to worry about air temps etc. I replaced my rigid copper lines with flexable hoses at the point just above the dryer, much easier to work with, works great, no more freezing up.

Grant

Chaz · January 21, 2010, 11:45:16 AM

I too am interested in adding an air dryer to my 4108. The AD9 seems like what most people suggest but I'm not opposed to using and older model if there is a benefit. (??)
I understand about the linear feet that need to be between the compressor and the dryer but in the engine compartment would be handy. Where are they normally mounted on a GMC ?? Would up front in the bay under the driver be a good spot?? Or in the old AC bay?? Just curious.
thanx,
Chaz

belfert · January 21, 2010, 01:23:46 PM

The only benefit to using an older air dryer than the AD-9 is cost if you can get an older model cheap. You can get used AD-9s from truck salvage places pretty cheap, but you'll probably be $100 into it by the time you overhaul a used one.

Bendix currently recommends the AD-9, AD-IS, or AD-IP for highway coaches. I have no idea what is different about a AD-IP or AD-IS.

The AD-9 is almost an industry standard for air dryers. Every truck or bus shop should have parts to fix an AD-9.

DaveG · January 21, 2010, 03:11:00 PM

I think I would stick with an AD-9. Anything older is not gonna be any more cost effective at a junkyard, and parts are probably gonna be the same...until they become obsolete...then newer is better. I think the newer ones have an integrated reservoir.

luvrbus · January 21, 2010, 03:36:12 PM

Guys you are not just stuck with Bendix other manufactures are out there also with cheaper replacement dessicant I like the Midland/Haldex and Wabco.
I don't like all the bolts on the AD 9 the old AD2 that came on my Eagle I can service it before you can get the bolts out of a AD9.

good luck

belfert · January 21, 2010, 03:56:33 PM

Yep, a lot of the AD-9s are not made by Bendix. I think my dessicant cartridge is not a Bendix I have in there now. I was never implying you had to get an AD-9 made by Bendix. Regardless of manufacturer, the AD-9 is still one of the most popular units out there today.

The bolts on the AD-9 don't bother me. It might add 10 minutes to the job. My main problem is it takes a whole afternoon on your back getting the thing out and back into the place they mounted the air dryer.