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Old 05-22-2015, 04:18 PM   #1
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odd noise, maybe airbrakes?

hi all,
i started hearing an odd noise after i turned off the bus about a week ago.
first time i ignored it. second time i heard it, i was like... dang.. that sounds odd. third time i heard it i started to track it down the noise.

after i turn off the bus and its no longer running..... it makes a buzzer noise. the buzz lasts half a second, but keeps going buzzing every minute or so for an hour after i turn off the bus.
the battery monitor shows no electric flow when the buzzer goes off and after looking under the bus.... it looks like its coming from an air tank.
as i was looking underneath the bus.... the rear brakes made a little swoosh like they were setting. i'd never heard that before either. the bus was off and parking brake set.

any wisdom appreciated

Dave
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Old 05-22-2015, 10:25 PM   #2
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I had a leaky treadle valve (aka "brake pedal") which made a slight hiss, and the air loss there caused a check valve elsewhere to hum/buzz lightly. Sometimes something in the area of my rear brakes make a buzz too. When it does happen it's usually just one time though and stops after a short time, so I've ignored it. Pressing the brake pedal firmly one time makes this noise on mine stop.

You can use a stethoscope, or a screwdriver or other rod/bar held to your ear, to help pinpoint the source of the noise.
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Old 05-23-2015, 01:58 PM   #3
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You can use a ... screwdriver or other rod/bar held to your ear, to help pinpoint the source of the noise.
The visual of this just struck me funny... Do you wear a tin foil hat too?
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Old 05-23-2015, 04:11 PM   #4
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The Jolly Roger has air brakes and after run time/brake system pressurized after I park he send's out a little toot about every5-minutes for an hour or so? But as I understand that is a pressure relief getting rid of unneeded pressure while in a parked or stowed position but he still maintains the pressure for the parking brakes? Not sure about your buzzing but with air brakes I think this my toot's are a good thing because in a pressurized system with rubber and plastic tubing/hoses the constant expansion/ pressure and the contraction/ bleeding pressure will show a problem and also help get rid of condensation in the air system better than a constant standing pressure on the system! The buzzing could be an electrical relay that tells that drain switch to operate and the valve is hung up and the relay is trying for a few second's but can't open the relief valve? The valve might be called an automatic drain valve?
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Old 05-23-2015, 06:20 PM   #5
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Originally Posted by Jolly Roger View Post
The Jolly Roger has air brakes and after run time/brake system pressurized after I park he send's out a little toot about every5-minutes for an hour or so? But as I understand that is a pressure relief getting rid of unneeded pressure while in a parked or stowed position but he still maintains the pressure for the parking brakes? Not sure about your buzzing but with air brakes I think this my toot's are a good thing because in a pressurized system with rubber and plastic tubing/hoses the constant expansion/ pressure and the contraction/ bleeding pressure will show a problem and also help get rid of condensation in the air system better than a constant standing pressure on the system! The buzzing could be an electrical relay that tells that drain switch to operate and the valve is hung up and the relay is trying for a few second's but can't open the relief valve? The valve might be called an automatic drain valve?
I think you should do some reading on how air brakes actually work.
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Old 05-23-2015, 07:44 PM   #6
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That noise you hear is the check valves bleeding off a bit from the "wet" tank into the primary and secondary tanks. Mine does that too, I just bleed of the wet tank and the noise goes away.
Asked a heavy truck mechanic about it and he said the valves were just talking to you.
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Old 05-24-2015, 06:28 PM   #7
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I think you should do some reading on how air brakes actually work.
What somewhereinusa means (among other things?) is that the parking brake needs air pressure only to release so that the vehicle can move. Large springs hold the brake applied indefinitely when the air pressure is released.
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Old 05-25-2015, 07:31 PM   #8
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Quote:
Originally Posted by family wagon View Post
You can use a ... screwdriver or other rod/bar held to your ear, to help pinpoint the source of the noise.
The visual of this just struck me funny... Do you wear a tin foil hat too?
Yes, the screwdriver/rod thing for finding chatty check valves is kind of like divining for water.. And in case it's been a while since you checked out tin foil hats, you should totally look again! There are some on Etsy for example that look really fashionable and comfortable!
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Old 05-25-2015, 08:03 PM   #9
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Still chuckling...
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Old 05-25-2015, 09:41 PM   #10
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Originally Posted by SassyLass View Post
The visual of this just struck me funny... Do you wear a tin foil hat too?
I used to use a broomstick held to my ear when adjusting valves on my 327 chevy, turn nut slowly until clicking went away then 1/2 turn more
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