SOLVED: Bus Won't Air Up

[GnarlyBus]

Started up the bus and it leaked out of the purge valve. The tapping trick didn't work.

So I removed the shield to get these pictures.

I think I'm gonna try to pull off the valve (don't have a socket or crescent wrench that big) and clean it.

I found a remain heater on there. Also found a tag that says 12v 60w. So the heater has been replaced with a 12v? Guess I'll rewire it.

Any other tricks than tapping it to get me down the road?

Can I remove the purge valve without removing the whole end cap?

Also, the governor was pushing air out the exhaust port the whole time while the bus was trying to air up. Is that normal?

[GnarlyBus]

Pulled apart the purge valve and nothing seemed wrong with it. Plenty spring left and the o-rings look good. I lived them up and put it back together. The stopper looked to be in great shape.

So maybe instead of sticking open, its being told to stay open by a faulty governor???

[Dave5Cs]

You could try cleaning the D2 governor or if you have the right fittings you could bypass the air dryer for now with a piece of hose. In other words connect the incoming (at the bottom)and the out going ( at the top) temporarily just make sure you drain the tanks regularly. I have had mine like that for 2 years with no problems but I don't live in cold country.

[GnarlyBus]

I guess I was a little early in calling this thread solved. I thought it was a simple sticky purge valve as that is where the air is gushing out.

What could cause the air dryer purge valve to be forced open when trying to air up the bus (works perfect when it does air up and go down the road)? It's not "sticking" or frozen, it's being forced open at the wrong time.

The purge valve is open and flowing when the bus is at 30 psi trying to air up.

It almost seems like the governor is in cut out mode and is redirecting the air to the dryer purge valve.

We've been moving down the road slowly trying to get as far as we can each day because we don't know when it's gonna decide to work again.

[lostagain]

Do you know how long ago the dryer was last serviced? How about the governor?

You should go to a truck parts store and buy a new governor, and a kit for the dryer that includes the desiccant cartridge and the purge valve with the heater and replace everything. That is routine preventive maintenance that should be done on a regular schedule. You will then have a fresh base line to run off of for the future. I would not carry on just by band-aiding an important system like the air system. You will find the overhaul directions on the Bendix web site. The parts are quite cheap, because they are made by the thousands for truckers and bus companies.

JC

[GnarlyBus]

These items have not been serviced in the 4 years I've had the bus. The air system is kind of the last area I'm learning. We don't drive the bus much.

I'll be replacing he governor sms dong an overhaul on the air dryer when we arrive in Oregon in a few days.

Just trying to better understand my issue so I don't get stuck somewhere in the next few days. I've read the air dryer and governor manuals in the last two days and am now reading the compressor.

Thanks.

[bevans6]

My bet is still the purge valve needing a kit.  If the governor was at fault, it would be unloading the compressor at the same time - and 30 psi is probably not enough air pressure to either unload the compressor or open the purge valve.  The mere fact that the compressor can build air and cuts out at 120 is pretty decent proof that the governor is working properly.

If you take the dust cover off the purge valve you can press direct on the valve to force it firmly closed, to see if that makes any difference to air leaking out. 

[Oonrahnjay]

... I'll be replacing he governor sms dong an overhaul on the air dryer when we arrive in Oregon in a few days.

Just trying to better understand my issue so I don't get stuck somewhere in the next few days. ...

     Someone earlier described how to completely bypass the dryer, and -- for a few days on a "get you home" basis -- I'd be leaning that way.  As described, just bypass the dryer with a piece of 1/2", or maybe 3/4" DOT hose* (and would the pressure line from the governor have to be blocked off???).

      Good luck with it.  It seems to me that a new governor (or a good rebuilt one) and dryer rebuild with solve this for you but you'll have to do what you have to do to get to Oregon first.

* 3/4" hose is not trusted a lot these days, but IMO if you have some that's undamaged, you might as well use it in the main air feed side, at least on a temp basis. 

[GnarlyBus]

My bet is still the purge valve needing a kit.  If the governor was at fault, it would be unloading the compressor at the same time - and 30 psi is probably not enough air pressure to either unload the compressor or open the purge valve.  The mere fact that the compressor can build air and cuts out at 120 is pretty decent proof that the governor is working properly.

If you take the dust cover off the purge valve you can press direct on the valve to force it firmly closed, to see if that makes any difference to air leaking out.

I removed the dust cover and pushed it closed. The bus aired right up. It's definitely the purge valve sticking.

[buswarrior]

The purge valve's natural state is to be closed. It takes an air pressure signal from the governor to trigger opening, and the resulting purge.

You will likely find it easier to disconnect and plug the signal line, than trying to disconnect both main lines, and then somehow connect them together, all without destroying the ability to put it all back together.

The purge valve will just stay shut, and then you can return it to service once parts are available.

Don't be running around with a compromised air system... stopping is kinda important...

Happy coaching!
Buswarrior

[buswarrior]

Oh, have you been draining the discharge muffler every day? Down the back, curb side engine access, "Drain Daily" mounted to the back of the tag axle wheel well?

And you'll have to put some special effort into getting the wet tank drained, once this excitement comes to an end to return your air system to dry.

Or you get to scream next winter about brakes stuck on...

Happy coaching!
Buswarrior

[bevans6]

BW has a great idea, disconnect the air line coming out of the center port of the air govenor ( the hose connection between the two mounting ports) and plug it, I think a 1/4 pipe plug.  Simple access through the door on the floor, probably under the bed.  That will simply disable the air dryer.  Push the purge valve closed, should be good to go.  What has probably happened is the O-ring around the top of the valve is sticky, not lubricated with correct silicon grease, or the internal spring has failed or lost sufficient tension.  The kit comes with new O-rings, a new valve head, a new spring and the correct grease.  And a few other parts.

[GnarlyBus]

Made it to our spot in Oregon!

So I have two weeks to do my repairs and maintenance.

I undid the control hose at the end cap of the air dryer and pushed the purge valve closed. My attempt at plugging the control line didn't work so it was open. Started up the bus and it aired up to 130 and stayed within 2-3 of that. When I pumped the brakes down to 80 to test, the psi built back up quickly.

So I made my way to Oregon. Kinda weird to me that it stayed at 130 the whole way (except when braking). Is that what you'd expect from an undone control line? Did I just male rd compressor run the whole time without a cutout?

[buswarrior]

Yeah, sounds like it ran the whole way.

Get it all fixed up, and forget about it...

Drain everything!

Happy coaching!
Buswarrior

[bevans6]

The open control line means that the unloader valves in the air compressor never got pressure, so the compressor simply ran for the duration, always pumping air.  You are lucky, I think, that it didn't rise to 150 psi and blow the safety release valve.  It really should have.  You lost all control over the air compressor by disabling the air governor.