Crud/oil in air brake tanks/lines

[Kwest364]

Bus:
1986 Chevy B6000
366cu in/6.0L V8
GAS
5 speed manual

My bus has 2 air tanks. The biggest is towards the front, driver side. Smaller behind the rear axles.

1. On each tank is a "key" thing that I can manually turn (pic). When I turn the keys, air rapidly shoots out of the tanks. When I barely turn the key, this goopy, brown, oil smelling stuff comes out. It comes out as long as I have the key turned. What is this gunk? Surely, there shouldn't be anything but air in these tanks, correct? How did this goop get in there? What IS the goop? WHY does it smell like oil?

2. On the front tank, in addition to the key valve, there is another purge valve of sorts near the bottom of the tank. ( pic). When I pulled on the cable that releases the valve, the same brown goopy stuff FLEW out. And it just kept coming, probably close to 500ml came out, gooey, gross, oil smell, all over my hand, then I just closed it.

WHAT is this? It's not supposed to be there, correct? Do I just keep purging the valve until that crap doesn't come out anymore?

What's the procedure for air brake purging/maintenance? Certain order of operations I need to follow? Specific steps I should take? Other maintenance to do? These aren't auto adjusting, I recently adjusted the slack out of them. But what else to do? Thanks

[cadillackid]

yep those are your air drain valves.. and the first one looks like an auto-moisture drain valve triggered possibly by when the governer shuts off though I dont see a small line going to it like i usually expect.



air comoressors have rings.. they are fed engine oil into their crankshafts and sometimes even an oil spray onto their pistons.. as the compressor wears a little oil here and there can seep by the rings and end up in the compressor cylinders..

that oil ends up pumped into the main lines and off to the first tank..



as air is compressed, its ability to hold moisture is reduced.. thus the moisture condenses as water on the inside of the air lines and that too goes into the Tank.. moisture is easily noticeable in humid conditions ie rainy days.. youll get lots of moisture in the tanks..



so when you open the drains you get a mix of that small amount of oil and the water and it all sprays out in a goopy mess!!



on more modern busses / trucks they have an Air dryer... (ever wonder what that Shhh!!! sound is you hear form big trucks?) its the air dryer purging that nasty mess out before it goes to the tank.. and its automatic..



on non Air-dryer trucks / busses you should open all of those drains nightly after driving and let that nasty mess out..


if you plan to drive this bus in COld (below freezing )weather.. installing an air dryer such as a Bendix AD-9 is a wise thing to do! it prevents that water from icing up and disabling the air brakes.. as it gets purged before reaching the tanks..

[Kwest364]

Thanks for the info. So I should just hold the tank valves open (they're both manual valves) until no more gunk comes out, correct?

The bigger valve: it has a cable attached to it to pull the valve open. End of cable is broken. I don't see where it came into the cab, but maybe it was attached to something where you could conveniently manually turn the keys. Seems like an awful design that a school bus driver would have to get directly under the bus, on the ground, to turn those keys. Maybe they all had something attached to turn keys manually from exterior of bus somehow, at one point? Idk

[cadillackid]

I have a 1978 SUperior on an International chassis.. and yep gotta lean under and open those valves.. I start front to back.. open one then the next and the last.. let em all go till they are empty then close em up..



when i start the bus next time i use it i check to make sure I closed them all the way and arent leaking as the compressor builds pressure..



Being a bus / truck driver meant (means) getting your hands dirty..



some trucks / busses had spring loaded drain valves with chains that were mounted over on the inside of the skirting.. youd simply pull the chain / cable to release..



similar to this..


https://www.napaonline.com/en/p/GRO8...&gclsrc=aw.ds&


I keep a box of Large 9 mil hardy plastic gloves and a bag of Harbor freight work gloves in each of my busses..






I keep a b