I started my bus for the first time in a few months, it builds about 15 lbs of air pressure and thats all, I operated the park brake and foot brake several times, not even enough pressure to shut the engine down, I listened for leaks heard a very faint leak at the air governor coming out of a small hole in the casting? any ideas?
Do you have a compressor you can connect to try and air the bus? If you do you'll be able to determine if it's a major leak somewhere or a problem with the engine's compressor/governor.
Richard, I do have shop air close by, that is my next step to air it up with that, this happened once before after sitting over the winter that time I just set the park break and it aired right up, not happening this time though. Thanks!
Quote from: goutoe on March 21, 2022, 08:18:39 AM
Richard, I do have shop air close by, that is my next step to air it up with that, this happened once before after sitting over the winter that time I just set the park break and it aired right up, not happening this time though. Thanks!
If you have no air, the park brake should already be set. Do you hear any air from the parking brake valve while you try to air it up?
I cant hear any leaks on the parking valve, but I can hear it set and release.
Get some "HEAT" at a auto store or truck stop etc. Take the big line loose from the compressor head and pour the heat in that hose and put it back on. Then try to start the engine and within minutes I woill bet it will start building air. Your system is frozen or rusted and this sometimes frees' it up. empty all tanks too.
Thanks Dave I will give that a try, I hear no leaks, I think something ts stuck.
A giant leak makes little noise from empty.
And that's a giant leak, only 15 lbs of air.
Broken supply hose, air drier purge valve come first. Then wonder about an obstruction. There will be very high pressure at the compressor outlet, if there is a stuck valve making an obstruction.
Pouring stuff in ahead of an air drier will turn the desicant into mud, if you think you got trouble now...
Happy coaching!
Buswarrior
And another question....
Is the air compressor working correctly?
Try taking the out put line lose and see what kind of pressure it's pumping out. If it's barely putting out any pressure it could the fiber gear that drives the compressor has given it up!
Seen this more than once!
;D BK ;D
Over the winter, the bus would note air up. It would get to about 30psi and no more. There are air leaks but did not have time to diagnose the source. When the weather warmed a bit or it decided to get off strike, it fired up and built pressure back up. Probably a sticky valve that got stuck when it got cold. Still need to sort out but at least back going again while it goes where it's warm which is fine with me.
If there is an obstruction the compressor outlet pipe should get pretty hot.
But the suggestion to connect air compressor is a good start.
I guess the best bet is to try the shop air if there are no apparent leaks then see what the compressor is putting out? I am still suspicious about the air governor, I could hear and feel air coming out of a small hole in the casting, is that how it is supposed to work?
I haven't tried this but there are a number of android apps for detecting gas/air leaks.
Ears and mechanics stethoscope will find 95% of them. Leak detector liquid or dish soap diluted for the slow ones.
Bull on the turning it to Mud BW.
I have done it before and it works. Dallas was the one who told me about it many years ago. It will wet the Desiccant but it will also dry soon with the air going through it. You can also just change the desiccant cartridge. If you can get to the other side of your air dryer then put it in there if worried about it, but they are always in a tough area to get to.
Thanks Dave, I bought some airline antifreeze that also has some lubricant in it, now I just have to figure out where I can pour it in to the system, I wanted to work on it after work yesterday but the weather wont cooperate! snowing now! but the weekend looks good I will tackle it then. Thanks for the help.
Hey John,
Keep in mind 12 smart guys are helping you solve this. The 300 other views are people like me that don't have a clue, but we are watching with great interest because it can happen to any of us. Please don't forget to tell us what worked. Guys like me that have been a bus owner for a mere 2 years take notes....
Hope you get it figured out.
Ted
Pull the air intake from the compressor and be sure the compressor is turning after the 15 lb they can strip a drive key and still pump 15lbs of air and a plugged air intake will stop a compressor from building air too
Ditto what Cliff said - that happened with our compressor - stripped drive and wouldn't pump above low psi.
Thanks Clifford, the intake would be the hose coming from the air filter housing, correct? I did connect to shop air yesterday, no leaks any where, I still can hear a very faint leak at the air governor coming from a small hole in the casting.
Will I be able to see if the compressor is turning though the intake? how do I inspect the drive key?
You can see if the unloader valves are working through the intake to inspect the drive the compressor needs to be removed
Thanks Clifford! Im going to power wash the compressor before I take the intake cover off, a bit cold for that today hopefully I will find a sticky valve but if I do need to pull the compressor it is very accessible.
Quote from: goutoe on March 27, 2022, 12:28:58 PM
. . .but if I do need to pull the compressor it is very accessible.
You have now discovered one of the advantages of having a V-drive powertrain! The alternator and air compressor are literally right there in front of you.
Not like the T-drive folk who have to become contortionists in order to access those items.
My guess is also the compressor drive may be stripped.
FWIW & HTH. . . ;)
RJ
Yeah, but Cliff thinks T drive are the best.😉
Quote from: chessie4905 on March 28, 2022, 07:50:18 AM
Yeah, but Cliff thinks T drive are the best.😉
You mean they are NOT? ;D
:D BK :D
Back in my previous bus days ('90s) I had a '68 GMC Fishbowl. We were parked in a Walmart lot in another state and had the same problem. It would only reach about 10-15 lbs. Turns out there was a truck supply outfit right across the street. I was able to get a new governor for about $15 and install it with an adjustable wrench in the Walmart parking lot. It's a pretty good chance that could be your problem.
Glennman I have been suspicious of the governor all along I can feel a small amount of air leaking from a small hole in the casing of the air governor I will check the intake as Clifford says, but I will try a new governor before I pull the compressor, My problem now is time to work on it !! hopefully this weekend I will get it figured out, Im also in the middle of installing a washer and dryer in the bus! and my wife is redoing all of the upholstery! I would love to post some pics of the progress but havent been able to figure that out yet!!Thanks to all of you for your help and concern! you guys are awesome, bear with me with your help I will get this Fixed!
Be careful with new governor. There are 4 holes, I think, and a set of Allen threaded plugs. Be sure to get them installed in same ports as old one.
well back to work on the bus today, checked the intake hose it was clear, took the intake housing off ran the engine no movement on the valves still only 15 psi so next is to pull the compressor, never done that before, I suppose it is on a spline? what do I look for next?? is there a key way?
Compressor has a drive cup on end. Remove bolts ant just take it off.
The cup gear attached to compressor is made of fiber bonded to steel core where it attaches to compressor. Normal failure is the fiber teeth strip off or the cup comes loose from steel core that bolts to compressor. Made of fiber so if fails, the fiber parts can go through engine gear train without gear damage. Easy to reinstall compressor. Just engage cup with sleeve gear teeth. That spring is there to stop in and out play of compressor crank attached to cup.
Quote from: chessie4905 on April 01, 2022, 06:48:52 PM
The cup gear attached to compressor is made of fiber bonded to steel core where it attaches to compressor. Normal failure is the fiber teeth strip off or the cup comes loose from steel core that bolts to compressor. Made of fiber so if fails, the fiber parts can go through engine gear train without gear damage. Easy to reinstall compressor. Just engage cup with sleeve gear teeth. That spring is there to stop in and out play of compressor crank attached to cup.
His drive will probably be the more up to date drive,I haven't saw that drive in years John :^
Pictured is the same compressor drive as we have - in failed, run, and have as a spare. Chessie's description is a good one.
Quote from: dtcerrato on April 02, 2022, 06:18:41 AM
Pictured is the same compressor drive as we have - in failed, run, and have as a spare. Chessie's description is a good one.
Those were prone for failure John is right ,the same drive that failed John Z on his 4104 in Texas Sonnie and Mike changed over to the newer drive in freezing weather
Thanks guys, My compressor is A BW if that helps? I did change out the air Governor as well, looks like a fairly simple job as mine is a V drive hopefully tomorrow I will have time to get the compressor pulled and have a look.
IMHO it's not like the old style fiber gear was problematic!
Heck in 43 years of same bus/engine ownership the compressor drive failed twice. The 1st replacement was brand new the current replacement (6 years now) is a part from an older bus and the spare part I carry is from an old bus. I'm okay with that. Purely mechanical & nothing catastrophic...over approaching a half a century! :^
When ours failed on the 4104, switched over to steel gear. Course if IT fails, major damage. Never had an issue though.
Detroit was always good when a problem area was causing problems to update to a better system or parts ,I still come across old DD the upgrades were never made,then they are not out beating the pavement for 100,000 miles a year either.Doyle installed a rebuilt blower on his 8v71 I told him he needed to update the blower drive naw he said it has worked fine since the 70's 4 days later I sent him the blower drive an parts he was broke down in Arkansas
After a thorough power washing I found an ID tag Bendix tho- 700 cant read the other nos. till I get the compressor off. Thanks for The pics and description Chessie that helps me understand what I'm looking at , I really appreciate that. John.
The biggest pain removing my compressor aside from its weight was plugging coolant lines quickly to avoid a mess. I believe the drive coupler in mine was all metal but its been a while since I had it off.
Quote from: fortyniner on April 03, 2022, 07:11:13 PM
The biggest pain removing my compressor aside from its weight was plugging coolant lines quickly to avoid a mess. I believe the drive coupler in mine was all metal but its been a while since I had it off.
When we're doing work that requires disconnecting coolant lines we lower the coolant by draining some of it off - a few to five gallons gallons should get it below the compressor.
The compressor drive coupler could be all metal - ours is but the female driven coupler (gear) on the compressor could be all metal or a combination of metal gear teeth with a fiber hub that could fail by "slipping" at above low PSI - it'll fool you unless you test it by locking the compressor from turning and putting a large channel lock on the "coupling" and try turning over the compressor - if you can with the compressor crank locked up - it's slipping but only under a load. We had one do that and it drove us crazy trying to figure - almost replaced the compressor but when we realized the driven gear was slipping we replaced it with an even older one - it's been 6 years in service w/o issue!
Dan thanks for the info, I wondered why it would build some air? I have the coolant drained down, and everything washed off, now just need the time to work on it. good thing is I dont need to use the bus till mid May! I am concerned about parts availability? John.
Luke's got them. And gaskets or whatever else
Chessie, I have seen posts referring to Luke But I don't know how to contact him do you have his info?? Thanks. John.
u s coach and equipment sales. Vineland new jersey. Luke is owner and the one that answers the phone.
he is on Facebook also.
Thanks Chessie! good to know!
Quote from: goutoe on April 05, 2022, 02:30:08 PM
Thanks Chessie! good to know!
What Chessie forgot to include is Luke's phone number: 1-888-262-2434
Put him in your phone contacts so you'll always have it!!
FWIW & HTH. . . ;)
RJ
I have the compressor on the bench it is just like the one in Chessies pics, I will try to make sure it is slipping while I hold the compressor from turning as Dan suggested, If is is slipping whats my next step? Do I remove the cotter key and nut to remove the drive? John.
I got the drive removed, looks like it was slipping, hard to tell by looking but I could see it moving between the fiber and the steel! I will call Luke Monday and get parts ordered! Thanks again for all of your help, I greatly appreciate it!! John.
Finally after a couple of months I found the problem, I had an air leak on a electric tank drain valve ,I could not hear it with the engine running, I finally hooked up shop air on the big line at the compressor, with the engine off I could hear a flutter, I replaced the valve and built air pressure right away! So I replaced the gear on the compressor and the air governor, A good trouble shooting experience. Thanks to all of you for your help with this issue. turned out to be an easy fix!!
What brand was the leaky one? Did you replace it with the same brand?
Wondering changing spring loaded to electric.
actually I replaced it with a manual valve for now, not sure what I want to use for a permanent valve ?