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Thomasbus24
Administrator
USA
4547 Posts |
 Posted - 03/22/2014 : 1:54:12 PM
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Need your help fellas. I have an 06 in the shop that has us stumped.
Push in parking brake, brakes release very, very slowly. All other brake functions are normal, including the release rate of the service brakes, so no foundation brake problem.
Have changed rear chambers (one was leaking), PP1, R12 and quick release valves, no change. PP1 does feel whimpy for lack of a better term when being pushed in. Like it isn't being supplied adequate air pressure.
What are we missing? |
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slippert
Top Member
USA
630 Posts |
Posted - 03/25/2014 : 11:56:52 AM
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Does the AAFE have an inversion valve on them? being an 06 seems like it would..
The inversion valve should be what gets signal/air pressure from dash valve and either releases park brake or dumps air out to set them... IR-2 Wabco/Meritor or Bendix R-7
This is from bendix air brake book.....
R-7 Modulating Valve
is used in dual circuit brake systems and
performs four functions; during normal operation, it limits hold-off
pressure to the spring brakes, provides quick release of air pressure
from the spring cavity of the spring brake actuator allowing a fast
application of the spring brake actuators, modulates spring brake
actuator application should a failure occur in the service brake system and prevents compounding of service and spring forces.
Otherwise unless you do have a supply pressure issue, (I.E. whimpy PP-1) may be getting enough pressure just not enough volume fast enough to make system work correctly..
you said they release slowly ...how fast do they set? |
Edited by - slippert on 03/25/2014 11:58:58 AM |
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Thomasbus24
Administrator
USA
4547 Posts |
Posted - 03/25/2014 : 3:28:22 PM
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Oh they set fast as lightening. Everything except releasing from park works just perfect.
The inversion valve is really all that is left...Napa is bringing one in the morning. |
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Thomasbus24
Administrator
USA
4547 Posts |
Posted - 03/26/2014 : 08:36:03 AM
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| Inverersion and quick release valve changed...problem still exists. Can of gasoline and a match? |
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slippert
Top Member
USA
630 Posts |
Posted - 03/26/2014 : 11:26:27 AM
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Gas and a match might be best option... Is this a lift bus with interlock system on it? not familiar with AAFE, but air brakes should be air brakes... systems should be similar...
I suppose if it was me.. I would trace the supply line from my pp-1 dash valve back to tank and see if it were blocked, pinched or collapsed? or system should have a double ck or similar valve in line or at tank where supply to pp-1 comes from? you did say dash valve feels weak... as air from tank should feed pp-1, then from there to inversion valve and on to chambers.. if your only problem is slow release...
System should have a double ck between the front and rear tanks to pull air from which ever one had highest pressure or both if pressure is equal for park brake... I am pretty sure the newer ones(at least IC's) use a pp-dc dash valve which has a double check incorporated in it...
Sounds like you have pretty much replaced everything except for lines and fittings... unless it has interlock system due to special needs bus then you add a few more checks and elecric solenoid valves to the mix! Good luck and I have extra matches if you need them.. |
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second.flood
Top Member
USA
640 Posts |
Posted - 03/26/2014 : 12:12:58 PM
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| Seems it would have to be a supply problem. Curious to know the fix. |
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Thomasbus24
Administrator
USA
4547 Posts |
Posted - 03/26/2014 : 1:41:49 PM
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No brake interlocks or anything cute like that. I'm off tomorrow, but I'll be looking at it more Friday. Check valves have been changed.
I will keep this updated for sure. |
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Thomasbus24
Administrator
USA
4547 Posts |
Posted - 04/01/2014 : 06:24:44 AM
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Nothing to update. We've done all we can easily do and decided to compare it to its twin. The twin operates the same way.
The driver of the bus says that it has changed since he got it, and be used to be a mechanics helper in the garage, so I'm inclined to believe him.
If you put the bus in drive, don't push the service brakes, and push in the parking brake, the bus moves in 3 seconds, even though the brakes haven't fully released. Does anybody think we are chasing problem that doesn't exist? Anyone have an 06 AAFE with air they are willing to check the release times? |
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1983WardFord
Top Member
USA
1395 Posts |
Posted - 04/01/2014 : 07:29:01 AM
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| Our Thomas EFs I had the pleasure of driving were like that. I don't know what type of system it was, though. |
Due to the current economic condition, the light at the end of the tunnel has been turned off until further notice. |
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Fastback
Top Member
1500 Posts |
Posted - 04/01/2014 : 09:07:48 AM
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quote:
Originally posted by Thomasbus24
Nothing to update. We've done all we can easily do and decided to compare it to its twin. The twin operates the same way.
The driver of the bus says that it has changed since he got it, and be used to be a mechanics helper in the garage, so I'm inclined to believe him.
If you put the bus in drive, don't push the service brakes, and push in the parking brake, the bus moves in 3 seconds, even though the brakes haven't fully released. Does anybody think we are chasing problem that doesn't exist? Anyone have an 06 AAFE with air they are willing to check the release times?
Just curious if the time till bus movement or release is any different in reverse?
Just thinking that the bottom shoe is the one that gets drawn into the drum when applied during forward vehicle movement and only has the return springs to pull it back, while in reverse it would be the top shoe and both gravity and return spring would draw it back. |
Why yes, the ORIGinal CHARGER is a Fastback |
Edited by - Fastback on 04/01/2014 09:09:52 AM |
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2006 BB AAFE air problem
