Time to school the new boy: air dryers

Paladin · October 26, 2007, 02:05:55 AM

Yesterday I asked about a rod sticking out in the rear of the bus. Air dryers were mentioned and I sort of know what they are but don't really understand them, at least not as I'm sure I need to so rather than pollute the other thread I thought I'd ask here in another.

Can people please teach me about what they are, where they are on an MC8, how many are there, what symptoms do they exhibit when going bad, what happens when they do, can they be rebuilt or do you buy them new, where and how much, are these items that should definitely be on a short list for good maintenance and if so, how often do you service them?

Really big thanks in advance,

-Dave

compedgemarine · October 26, 2007, 07:40:52 AM

hey Dave
as the compressor compresses the air it builds heat. the air then moves throught the system and begins to cool. as it cools the moisture in the air turns to water. the air dryer is the first thing in line and collects the water and dumps it out. if you go to the Bendix site there is all kinds of info.
steve

compedgemarine · October 26, 2007, 09:26:07 AM

try this link if I did this right.
http://www.bendixvrc.com/itemDisplay.asp?documentID=4631

JohnEd · October 26, 2007, 11:51:22 AM

Steve,

GREAT reference! Thank you! Now I can understand the explanation I am given by the "corp memory" on the board. They know what the failure symptoms "mean" cause the Bendix only describes what a functioning system acts like. I hope you are one of those guys. Lost without the first half, though.

Thanks again,

John

Frank @ TX · October 26, 2007, 12:46:24 PM

Hi John,
If the dryer if going bad if will pass water to the first tank.
You will not know that lots of water is in the tank until you pull the ring to dump the tank.
My dryer is working good 'cause when I pull the rings no / very little water vapor comes out.
Hope this helps
Frank

compedgemarine · October 26, 2007, 02:25:48 PM

Hey guys,
one of the biggest problems with the air dryer is that it is "out of sight out of mind". so long as nothing fails people tend to ignore it. it is recommended that the dissicant cartrage be replaced every year but rarely is. also some of the older ones are hard to get parts for. thats the reason I just bought a new dryer. besides being easier to service it also has parts availible just about anywhere you go. also on the second and all other tanks, they are supposed to be drained everyday when the vehicle is being used.
hope some of this helps.
steve

Paladin · October 26, 2007, 02:30:22 PM

Quote from: compedgemarine on October 26, 2007, 09:26:07 AM
try this link if I did this right.
http://www.bendixvrc.com/itemDisplay.asp?documentID=4631

Fascinating reading and I'm still reading over it. Great info, thanks!

Where though is my dryer on my 8?

-Dave

compedgemarine · October 26, 2007, 03:23:33 PM

cant help on that but everyone keeps saying that the MCIs have them in front so I would assume it is somewhere you can see it. either in front of the axle up front or under the driver area? some one here should know.
steve

buswarrior · October 26, 2007, 07:55:35 PM

hello

up under the front axle, bolted to the front wall, the air tanks are bolted to the rear wall.

It should make a sharp purging noise and blow a hole in the gravel directly below it when the air system reaches cut out pressure, typically somewhere above 120 lb.

Desicant need only be changed according to duty cycle. In commercial service, it would not be unreasonable to change it out annually, typically in the fall for those of us up north.

In a bus conversion, many of us don't run enough in 5 years to wear the desicant out.

That being said, it all depends how much air you have put through it, so if you drive a leaky teaky, your mileage may vary....

happy coaching!
buswarrior