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Author Topic: Time to learn the air system  (Read 675 times)
Dawgs
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« on: January 18, 2015, 03:40:19 PM »

I was going to move my bus into the barn today but the most I could get out of the air system was 85psi.  Not enough to lift her up.  I listened for leaks and it still had air after 5 hours.  The only tank I know to drain is under the drivers seat and it drained normally and a valve at the rear of the bus near where the lav holding tank used to be.  I figured it was froze up some where last month.  Temps here the last couple of days have made it to 60.
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Jim D
1986 MCI 102A3  6v92
krcevs
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« Reply #1 on: January 18, 2015, 04:09:18 PM »

There is 2 reasons that your bus isn't building pressure if the system is not frozen up. 1 is that the governor is causing it either the cutout spring has given up and you will need to replace the governor to fix this problem, or  the compressor valve that unload the compressor have gotten stuck and will need to be cleaned. This also requires removal f the governor from the compressor. The valves are located behind the governor. easy to clean, just use brake cleaner and work the valves up and down a bit.
Hope this helps.

Ken
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Kim and Ken Carpenter
GMC PD4107-1121
Berthoud CO
Oonrahnjay
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« Reply #2 on: January 18, 2015, 04:37:26 PM »

    I took the Bendix Brake School (5 days of classes) a couple of years ago.  Best $300 I've spent in a long time.
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Bruce H; Wallace (near Wilmington) NC
1976 Daimler (British) Double-Decker Bus; 34' long
6-cyl, 4-stroke, Leyland O-680 engine

(New Email -- brucebearnc@ (theGoogle gmail place) .com)
buswarrior
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'75 MC8 8V71 HT740




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« Reply #3 on: January 19, 2015, 12:06:15 AM »

In trouble shooting air issues, the devil is in trying to hear air escaping if it is.

If you get to 60 degrees outside, I doubt the coach is frozen.

You need to figure out if the compressor is trying to fill the system. If it is, the air is obstructed or leaking. If it isn't pumping, as noted, the governor is the first check.

In your case, I would be curious about air escaping while the engine is running, since it isn't leaking sitting.

Condition of the big flex line off the compressor? Do you have a lazy air drier purge valve?

If your ears aren't there, find a kid to help!

I am always hesitant to start using tools too early, making new problems for myself.

happy coaching!
buswarrior
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Frozen North, Greater Toronto Area
bronson
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« Reply #4 on: January 19, 2015, 04:13:11 AM »

Try this Bendix site. It is free. http://www.brake-school.com/public/
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Gary Bronson
1984-MCI-9
Mount Orab Ohio
Dawgs
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« Reply #5 on: January 19, 2015, 02:21:09 PM »

I also am a big believer in trouble shooting!!  I am new to the world of busses and just trying to learn where everything is located.  I started her up again today to start looking and listening.....next thing I know she is starting to lift herself up.  I jump inside and she is sitting at 120psi!!  I did find the big "wet" (I think) tank, just aft of the rear bay.  I'm kinda Leary about crawling under there and pulling the ring.  I know without air she sits low.  Now to find the dryer.

Gary, thanks for the link!!
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Jim D
1986 MCI 102A3  6v92
buswarrior
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'75 MC8 8V71 HT740




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« Reply #6 on: January 19, 2015, 05:02:47 PM »

Dawgs, up in the front axle cavity, do you have two tanks? The wet tank is up there, IIRC. You might find the drier up there too. Darn, I hate being out of practice...

I applaud your safety mindset! There are 4x4 wood blocks you can slip into the suspension to defend against unexpected lowering, and then a build up of lumber under the axle to rule out the tires.

I would be VERY suspicious you are dosed in water and trouble will return with cold temps.

Drain the discharge muffler down the back in the curb side engine door. Do you hear the air drier purge when the coach reaches the. ~120 lb cut-out?

happy coaching!
buswarrior
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Frozen North, Greater Toronto Area
Dave5Cs
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1979 MCI MC5Cs 6V-71 644MT Allison, Roseville, CA




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« Reply #7 on: January 19, 2015, 05:10:30 PM »

Dawg the dry tank should be on the left rear bay against bulkhead. Up front by Air drier there is also an air system filter. It is a string type and luke should have it.
Dave
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My personal skills are fine.. itís my tolerance to idiots that needs work!....

http://s1264.photobucket.com/albums/jj493/fltmr2000/
Dawgs
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« Reply #8 on: January 19, 2015, 07:34:14 PM »

Thanks guys!!  I'm learning.....slowly but I am learning.  I haven't heard the air dryer purge.  I only noticed one tank up front.
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Jim D
1986 MCI 102A3  6v92
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