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mrfrigabear
New Member

5 Posts

Posted - 11/02/2012 :  11:39:20 AM  Show Profile  Visit mrfrigabear's Homepage  Reply with Quote
I have a bus that when driving slow as approaching a stop sign or railroad crossing, the parking brake comes on and will not release. My repair shop has been unable to find the cause and can't duplicate the problem on a test drive. It's only when going slowly. The last time we started and shut off the bus several times in order to get the brake to release. Several codes were address, all without resolving the issue. Any thoughts?

eddo
Senior Member

USA
88 Posts

Posted - 11/02/2012 :  1:18:33 PM  Show Profile  Reply with Quote
Year and model? Air brakes? Hydraulic?

I have an '06 1300 with hydraulic brakes that would do this randomly. It was the brake motor, and was replaced under warranty. In fact, IH and WABCO extended the warranty of these motors to 5 years. and they have had tons of problems with them.

http://www.schoolbusfleet.com/forum/topic.asp?TOPIC_ID=23513


Edited by - eddo on 11/02/2012 1:19:02 PM
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mrfrigabear
New Member

5 Posts

Posted - 11/12/2012 :  10:26:21 AM  Show Profile  Visit mrfrigabear's Homepage  Reply with Quote
Sorry for the delayed response. Its a 2004 IC CE300 with hydraulic brakes.
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mastertech
Advanced Member

211 Posts

Posted - 11/12/2012 :  4:40:23 PM  Show Profile  Visit mastertech's Homepage  Reply with Quote
The most common issues with those are the resistance values in the parking brake switch change and the sahr can coil goes bad which can cause problems like you have. You should get a code though. If the motor stop working Ive never seen them restart on their own without smacking them . You would for sure get a code for no pressure in the front rezzy.
When we first got those vehicles I believe wabco had a new program to install to keep them from applying the brakes while the bus is driving.
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Dvorak
Senior Member

United States
52 Posts

Posted - 11/13/2012 :  03:36:28 AM  Show Profile  Reply with Quote
We had an issue with one of our 07 CE's that sounds exactly like this scenario. Our problem was rusted tone rings on the rotor. When the bus was coming or leaving a stop sign, very intermittently the service brakes would apply. The reason this was happening is that one of the rear speed sensors wasn't picking up a signal from the rotor making the HCU think that one of the tires was spinning and the other wasn't moving. The traction control system then applied brake pressure to the wheel it thought was spinning in an attempt to transfer torque to the opposite wheel. Obviously on dry pavement this will stop the vehicle dead in it's tracks. The fix for this problem was to put performance friction rotors on all 4 corners.

We initially thought the park brake was causing our problems as well. We realized that wasn't the case when we cut the short cable to get it out of an intersection and the service brakes applied while trying to move it again. Is your park brake light in the dash coming on when this problem happens? How about your ABS and Traction Control lights?

Hope this helps.
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mrfrigabear
New Member

5 Posts

Posted - 11/16/2012 :  09:33:56 AM  Show Profile  Visit mrfrigabear's Homepage  Reply with Quote
quote:
Originally posted by mastertech

The most common issues with those are the resistance values in the parking brake switch change and the sahr can coil goes bad which can cause problems like you have. You should get a code though. If the motor stop working Ive never seen them restart on their own without smacking them . You would for sure get a code for no pressure in the front rezzy.
When we first got those vehicles I believe wabco had a new program to install to keep them from applying the brakes while the bus is driving.

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mrfrigabear
New Member

5 Posts

Posted - 11/16/2012 :  09:36:19 AM  Show Profile  Visit mrfrigabear's Homepage  Reply with Quote
Thanks for the info
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