534 Air Brake problem

Robvan · #1 (**permalink**) 12-16-2008, 10:36 AM

Have 77 535 or so Cab over Bluebird School bus/motor home on propane with air brakes,

It freezing, A lot colder than normal, Suspect the air system freezing up,

Tail lights won't go out when the engine's off or slow to release, disconnected the battery and when hooked up again and running went out, but came back on again shortly later without any air built up, The Air drier?, pop off valve (canister behind front axle) leaks to the point it won't build air, or only build enough to get/keep the maxi off, (gauge actually reading 55lbs, and wig wag low air flag not staying up, but still having 70-80lbs available on brake application ?)
Last time I put a heater under the drier for a bit, then after running about 20 minutes everything went back to normal, But expect this is going to happen again.

Anyone know where and what to add into the system to avoid freeze ups of the air system?

In logging camps we used to use Methyl hydrate in most of the heavy equipment, And sometimes some kind of mineral oil (old junk without air driers) but not sure where it was added, The compressor and lines on this one very hard to get at, but there some small lines on top of the engine,
Also not sure if it should be done on this with what appears to be an air drier.

94Sport5sp · #2 (**permalink**) 01-08-2009, 10:57 PM

Hi:

Out truck is a 73 C900 with a 477 motor. On the back of the motor there is a canister where some air brake antifreeze can be added. As the compressor runs, it draws in some antifreeze and this antifreeze air mixture prevents the brakes from freezing. Another option is to add an air brake dryer similar to what can be found at Meritor WABCO -- Products -- System Saver Air Dryers but given where you live you may not frequently need this item.

PaMnd

Robvan · #3 (**permalink**) 01-09-2009, 12:14 AM

Thanks,

I haven't seen anything like that on the back of this engine, or crawled under it to look for something, but there some other odd components I can get to from the top I yet to check my air brakes manual to figure out what they are and if suitable to add something to the lines.

But, I also haven't had any problems since, and run a few times in as cold a weather. But not shutting down till after the compressor cycles and pops off the excess pressure and maybe the excess moisture that I think was creating the problem.

Looks like I have a Bendix AD-2 air dryer already, probably just needs a new cartridge or other servicing.... eventually.
It looking pretty old to the point It'll probably need a new bracket and fittings taking it off to service if I have problems, or end up needing to replace the entire unit and air lines to it,......or just stick a heater under it if it screws up again.