Reply
 
Thread Tools Display Modes
 
Old 03-26-2006, 07:51 PM   #1
Skoolie
 
Join Date: Nov 2005
Posts: 213
Air Brake Guru's ??

Any air brake guru's here?

My system was working fine until the other day I took it for a ride and noticed the compressor keeps cycling, it runs until you hear the blow off blast a shot of air under the bus then 10 seconds later the compressor is running again until it builds enough pressure to blow off again, the compressor usually only has to run 20 -30 seconds before it blows off the blast of air that comes out the drier? (canister like a coffee can)

I took the intake filter and bracket off the compressor and watch the unloader work it seems to be ok, I removed the governor on the compressor and it was clean inside so I dont think its the problem.

Thanks in advance.
hoser is offline   Reply With Quote
Old 03-26-2006, 07:56 PM   #2
Bus Geek
 
lapeer20m's Avatar
 
Join Date: Nov 2003
Location: near flint michigan
Posts: 2,653
what's the pressure gauge read before the compressor kicks on? when it shuts off?

can you hear air escaping from anywhere? Try it with the parking brake on, then with it off (chock the wheels obviously so you don't run yourself over)

how long does the system stay up to pressure after the bus is shut off?
__________________
Quis custodiet ipsos custodes (who will watch the watchmen?)
lapeer20m is offline   Reply With Quote
Old 03-26-2006, 08:02 PM   #3
Skoolie
 
Join Date: Nov 2005
Posts: 213
Quote:
Originally Posted by lapeer20m
what's the pressure gauge read before the compressor kicks on? when it shuts off?

can you hear air escaping from anywhere? Try it with the parking brake on, then with it off (chock the wheels obviously so you don't run yourself over)

how long does the system stay up to pressure after the bus is shut off?

I will look tomorrow on the pressure for an exact reading but I think its blowing (hear it blow off under bus) off at about 125 psi, dont see the gauge drop any when the unloader drops and the compressor starts compressing air again, bus can set 7 days and only drop 10 psi no major leaks that I could find.

Gut feeling is a control is out of whack, dunno how it could self adjust so assume it something gummed up?

Reading up on the system at http://www.bendix.com/troubleshooting/index.do

Thanks again
hoser is offline   Reply With Quote
Old 03-26-2006, 08:27 PM   #4
Bus Nut
 
frank-id's Avatar
 
Join Date: Nov 2003
Location: Twin Falls, Idaho
Posts: 808
From where I am sitting,

It would seem the govenor is fussy or tired. If this control is exposed to water, the unloader valve will stick closed. It acts as tho the compressor will pump up till the pressure relief valve opens. Go get a rebuild control for about $35. If possible, try a govenor from another bus. Most govenors are preset to about 120 PSI. The govenor controls the compressor valves. Some truck/bus drivers turn up thebrake system's pressure in an attempt to make the brakes perform better. This does not improve braking. Braking is only improved by adjusting the slack adjustera at each wheel. Fraqnk
frank-id is offline   Reply With Quote
Old 03-26-2006, 08:27 PM   #5
Skoolie
 
Join Date: Nov 2005
Posts: 213
"""The air dryer is an in-line filtration system that removes
both water vapor and oil droplets from the compressor
discharge air after it leaves the compressor. This results
in cleaner, drier air being supplied to the air brake
system, and aids in the prevention of air line and
component freeze-ups in winter weather.

Air dryers typically use a replaceable cartridge
containing a desiccant material and an oil separator.
Most of the oil droplets are removed by the oil
separator as the air passes into the air dryer. The air
then moves through the desiccant material which
removes most of the water vapor.

When the air pressure in the supply air tank reaches
the required level, the governor makes the compressor
stop building air and allows the air dryer’s “purge cycle”
to begin. During the purge cycle the desiccant material
is regenerated (its ability to remove water is renewed)
by a reversal of the saturation process. A small amount
of dry air passes back through the desiccant material
and the water that has been collected, as well as any oil
droplets collected by the oil separator, are purged out
through the base of the dryer. It is normal to see a
small amount of oil around the purge valve.""""

Sounds like the system is operating normal with the exception of the never ending cycle, I guess I need to install a accurate gauge close to the compressor and see what the exact cut in and cut out pressures are.
hoser is offline   Reply With Quote
Old 03-26-2006, 09:26 PM   #6
Skoolie
 
Join Date: Nov 2005
Posts: 213
Re: From where I am sitting,

Quote:
Originally Posted by frank-id
It would seem the govenor is fussy or tired. If this control is exposed to water, the unloader valve will stick closed. It acts as tho the compressor will pump up till the pressure relief valve opens. Go get a rebuild control for about $35. If possible, try a govenor from another bus. Most govenors are preset to about 120 PSI. The govenor controls the compressor valves. Some truck/bus drivers turn up thebrake system's pressure in an attempt to make the brakes perform better. This does not improve braking. Braking is only improved by adjusting the slack adjustera at each wheel. Fraqnk
I removed the governor from the compressor and took it apart on the bench, removed the dust cap in the adjuster end, I removed the snap ring that retains the adjuster assembly and piston, after removing the adjuster and spring assembly I found some, clean, old oil that, was kinda sticky like it had varnished, I cleaned that out with my finger and a rag then sprayed some PB Blaster air tool oil into the bore as a lube and tapped the body in my hand until the piston made its way to the open end and I could pull it out with my fingers, once out the O rings looked a little worn, more square than worn but still looked to be in good shape, the springs on the internal valve with in the piston body itself seem to work ok, I sprayed the whole assembly with the PB blaster air tool oil to clean it up, the bore and body of the governor, I sprayed it out good with carb cleaner and compressed air then lubed it again with the PB Blaster air tool oil and assembled the valve, it seem to slide in ok nothing rough or real loose.

I guess tomorrow I will remove the governor again and look closer at the small springs in the piston that are some sort of a valve (not 100% sure how this part works yet need a schematic) to ensure none are broken, I think that assembly sends a signal to the dryer to purge off any water and oil? I will also at this time replace the two O rings on the piston.


Thanks again for the help, any other thoughts?
hoser is offline   Reply With Quote
Old 03-27-2006, 02:07 PM   #7
Skoolie
 
Join Date: Nov 2005
Posts: 213
Ok looking at the dash gauge its kicking off at 118 lbs + or - a few lbs

I turned the adjuster on the gov in 1/4 turn and it raised the cut out pressure to about 130 psi, it still cycles the same.

Is their another component in the system that could be back feeding pressure to the governor and fooling it into running the compressor longer making it short cycle? Again not seeing any pressure drop on the dash gauge.

Thanks again.
hoser is offline   Reply With Quote
Old 03-31-2006, 11:29 PM   #8
Almost There
 
abdabbs's Avatar
 
Join Date: Jul 2004
Location: Iowa
Posts: 73
Year: 1984
Coachwork: BlueBird
Chassis: Ford B700
Engine: orig.327, now 429
Rated Cap: 66
Send a message via ICQ to abdabbs Send a message via AIM to abdabbs
governor

Just though I would pipe in my two cents.

To start, I had the exact same problem with my air brakes that you are having. I had people look at it and tell me that there seemed to be a leak on the exhaust side somewhere..... I dont think they knew jack personally.

Anyway, after installing my 'new' engine this last year I made the mistake of not completely checking the oil intake line from the oil pump. Well... I fried my compressor and bought a rebuilt one. Upon picking it up at the shop and having a new oil line made the guy asked me if I needed a new governor for it. I said that I was just going to use the old one and he said that I was crazy for not spending another 30 bucks or so and getting a new one. I bought one and after installing everything back up I have not had one single problem with blow off at all.

I dont know if this will help any but you seem to be going thru a lot of work with your governor vs spending 30 or so bucks for a new one. And although you may not have a oil problem with your compressor, I would also recommend spending the 10 bucks or so and have a new oil line made. I wish I had and I couldve saved myself an extra 360.00 on my engine install.

TonyC in Iowa
abdabbs is offline   Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
To the tire Guru's somewhereinusa Skoolie Conversion Projects 3 11-13-2014 01:29 AM
air brake 101...or how to fix/diagnois a stuck brake issue bansil Conversion General Discussions 16 06-28-2012 03:28 PM
Air Brake Help??? talk2cfs Ford Drivetrain 1 07-31-2010 08:12 PM
Need A Ford Guru....... paul iossi Ford Drivetrain 6 12-08-2009 09:26 PM
Questions for the seasoned BUS GURU'S Papabear Mechanical and Drivetrains 14 11-05-2009 10:32 AM

» Virginia Campgrounds

Reviews provided by

Powered by vBadvanced CMPS v3.2.3

All times are GMT -5. The time now is 05:32 PM.


Powered by vBulletin® Version 3.8.8 Beta 4
Copyright ©2000 - 2017, vBulletin Solutions, Inc.