air up issues

[white-eagle]

We're havin trouble leavin Arcadia, Fl.  Our bus, we thought, was working fine.  We left, got to a diesel pump 20 mi away, and were too low on air (60lbs.) to release the brakes and get out of the fuel line.  They were at 60 lb and wouldn't move up.  My pancake air compressor supplied enough air to get to 120lb and back to Jack's, but i was down to 90.  aired down further with the brake to about 80 where it should have kicked back in, but didn't.  For whatever reason, i let the air out using the air connector by the battery compartment, which lets air only out of the front tank.  Down the 30 lbs, rear still at 90.  But this time it aired up.  i hit the brake to get it back down, both tanks, to 80, then 70.  nothing, no kick in.  let the air out again on the front tank, and we aired up ok.  The fourth time i was hitting the brake to let air out, and seeing if it would kick in, it did, at about 80 lbs.  Seemed to work normally after that.
Jack and i theorize that the governor was stuck because we had not let it work down to 80, then back up while actually driving for almost 3 weeks.  now that we exercised it, it's back to working right.
We're planning on installing a new one tomorrow, and keep the old one for a spare.

i'm looking for other theories or knowledge so that we don't change the wrong part out.

[fredcliff]

we just went through the same issues it sounds like you leveler valve is causing a problem

[luvrbus]

I don't think it a leveler valve on his Eagle lol,Tom disconnect the 1/4 line from the air dryer if airs up normal service the air dryer you know where it is at sounds like the purge valve lol


good luck

[Ace]

We had a very similar situation with our bus when we first got it and it was the air drier. We had horizon coach (Alley) fix it for us and he said it was a near to get to and hoped we never brought to him for that ever again. If I remember right, it was pretty costly too!

[white-eagle]

i changed out the air drier thing a ma jig a couple years ago when someone said the frozen lines that we may have had, were due to condensation. and i put the new kit in for the discharge. 

i don't understand why an air drier would keep it from airing up until it got below 30 lbs, then allow it to air up to 120.  seems to me the governor isn't kicking in on time.  Not saying you're not right, but it's not yet logical to me, i dont' understand.

ace, it was a bear to undo all the bolts, and not really in an easy place.  He probably charge $50 for the labor and $200 for agravation 

[Chopper Scott]

Governors are cheap and generally worth looking at first. To bad you can't change the air leveler valve on an Eagle and make it ride like a MCI!!!

[buswarrior]

From the story thus far, I am assuming that the age of the governor is unknown?

From that, and the symptoms, change it out first and call it preventive maintenance.

Problem gone? job done.

If it sticks once, it'll stick again, only worse the next time...

As for air driers...

The air direr purge valve, when in the purged position, by its function, closes off the line beyond the air drier to the tank. If the purge valve sticks, typically from being frozen by a faulty heater, you get no air further downstream. You can diagnose this if you have a discharge muffler and drain between the compressor and the air drier. There will HUGE amounts of air in the line at the muffler, and none reaching the tanks.

Wake up southerners who went to sleep when I typed freezing...The other thing besides freezing can be intruders into the purge valve if the rubber exhaust diaphragm is missing. Those mud nest creating flying beasties, mud daubers and the like, are the devil. Fill the space with mud, and then it can't move.

happy coaching!
buswarrior

[white-eagle]

age of the governor is unknown-true.  relatively easy to change-also true.  But i now better understand how the air drier can be an issue.  Last time i took the whole thing out and the hard part was reaching the darn bolts, not actually fixing it.

thanks Ace, Clifford and Ewan(?sp).

[eddiepotts]

The last time I rebuilt my drier I never took it out of the bus. I have the AD2. I took the retaining bolts off the bottom and used a floor jack and a hammer handle to take the pressure off the keeper ring and everything fell out the bottom. Now that I have done it once It is probably about an hour job to do right on the bus.

[bevans6]

Part of the daily inspection before driving the bus is to have the air pressure all the way up, and to fan the brakes down to around 80 psi on the gauge.  With the engine at high idle or 1000 rpm, observe the governor engage to build air pressure, and time the rise between 85 psi and 100 psi.  that needs to be less than 45 seconds and typically between 18 and 30 seconds.  That is a DOT test that any air-braked vehicle needs to be able to pass.

Hopefully it's just a governor change and on the road again.  I need to change mine out as routine maintenance this spring.  Did your low air warning sound off?

Brian

[luvrbus]

All the years I have owned buses I never had a governor go bad always changed it with a new compressor change but never a problem any other time maybe lucky lol


good luck

[JackConrad]

White-Eagle is back on the road. We replaced his governor this morning.

Bevan,
   Tom did a full pressure check yeterday morning before leaving our house and everything worked as it is supposed to. Problem occurred when he stopped for fuel and restarted the engine. The low air buzzer did not come on iniatially because his pressure was at 70, but not increasing.  When he pumped the brakes to lower the pressure, the buzzer came on (about 60-65 PSI).  After installing the new governor, we did another complete air sytem DOT check, including pumping down the brakes to insure the spring brakes would apply(about 45-50 PSI).  Jack

[bevans6]

Jack, that's good news and proof that sometimes things happen at the gas pump! Or any other place, you always have to be watching.  Really nice that everything worked as it should and worked out well.  My comment was to remind people that it's possible to test for this very condition, and that you can do it while you are airing up the bus in the morning.  I actually note the compressor recovery time, and the fact that I do the other air tests and what their results are, in my notebook every time I do them, so I can have a record of what it happening or changing over time.

BW, I had a question about the idea of a sticky purge valve on the air dryer.  I agree that when it is in the purge position, no air can pass to or from the wet tank.  But if it's stuck and the governor engages the compressor to supply air, wouldn't that air just vent out the purge valve if it was stuck open?

Brian

[JackConrad]

BW, I had a question about the idea of a sticky purge valve on the air dryer.  I agree that when it is in the purge position, no air can pass to or from the wet tank.  But if it's stuck and the governor engages the compressor to supply air, wouldn't that air just vent out the purge valve if it was stuck open?
Brian

I am pretty sure that is correct. The air dryer on his bus is close enough that we could listen for air leaking from it. There was no air leaking from the dryer exhaust valve.  In fact we could not hear any air leaks anywhereon the bus.  Jack

[buswarrior]

Whenever I have dealt with frozen purge valves, there's no leaks. The pressure just builds to where the compressor can't build it any higher in the line between compressor and air drier.

You'll get a rush of air out of the discharge muffler drain like you've never had before.

That's the devil, you have no air, and there's no noises of leaks.

Then a little knowledge runs wild in the imagination of all sorts of broken bits...

happy coaching!
buswarrior