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peter2019
Senior Member
125 Posts |
 Posted - 05/26/2020 : 09:55:55 AM
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Hi, 2006 international school bus hydraulic brake - Wabco, due to COVID-19 didnot move for almost a month, after bus start today, brake pressure, ABS warning light doesnot go off, use tool box got code: SID 60 FMI 10, Pump Motor Rear - Low pressure gradient. Looks like only front brake working, rear brake doesnot work, difficult to release parking brake. Please help, Thanks!
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exmod110
Senior Member
152 Posts |
Posted - 05/27/2020 : 12:05:29 PM
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go under the bus and hit the hcu with a rubber mallet. (not the ecu attached to it)
Keep trying as after sitting they do strange things.
Remove the res cap too. they get plugged up and prevent pressure build up. |
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peter2019
Senior Member
125 Posts |
Posted - 05/27/2020 : 7:12:43 PM
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| Thanks for reply, exmod110, you mean hit the base where two pump motors attached , is that right? and remove the master cylinder cap as well, right? |
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exmod110
Senior Member
152 Posts |
Posted - 05/28/2020 : 06:51:52 AM
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yes and yes. we have had the res cap plug up and give long build up times setting the pressure gradient code b4. it can not draw air into the res as the pumps try to fill the accumulators causing a low pressure in the res. typically happens when its -30 but its an easy thing to rule out.
You should hear both motors when u either hit the brake or turn the key on. you don't have to hit things hard if its just hanging up from sitting. do this key on engine off while they are doing the initial build up, you will hear the motor noise change if it frees up. if you do not hear the motor noise change chances are you will be needing an HCU replacement for a seized motor. I do not know if the pump motors are serviced separately. |
Edited by - exmod110 on 05/28/2020 06:53:53 AM |
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TRex
Senior Member
97 Posts |
Posted - 05/29/2020 : 1:54:26 PM
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| Cap part # 2587199C1. Just had one of these. Opps. Goota go will post more later. Short story, try pressure bleeding it. |
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peter2019
Senior Member
125 Posts |
Posted - 05/29/2020 : 4:15:28 PM
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Hi Exmod110, I did what's you said, used mallet to hit the HCU, even pump as well, and remove master cylinder cap, but looks like not really working. After I turned the key on and off more than 20 times, I can see from toolbox(software) showing rear axle pressure slow building up, then brake pressure warning went off! Great news! but I donot think the problem gone because warning will come back again after driving if I press brake paddle few times, it looks like rear motor pump build pressure much slower than the front motor pump, does it mean I need replace rear motor pump? Thanks!
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exmod110
Senior Member
152 Posts |
Posted - 06/01/2020 : 05:00:14 AM
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you can command the pumps on seperatly with tool box i believe. do they sound the same? only other thing you can do is confirm the motor is getting a full 12-13 volts and has good ground (load test the circuit), check the motors resistance compared to the front motor, if all in spec replace component.
You can try bleeding it like TRex mentioned just to rule out any air in the rear side system. another cheap and easy thing to rule out. |
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TRex
Senior Member
97 Posts |
Posted - 06/09/2020 : 09:18:36 AM
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anyway pressure bleed it per the WABCO manual I think most current is MM-0401 revised 08-18.
http://graphicvillage.org/meritor/MM0401.pdf . It is not spelled out in here but the system knows if it doesn't have fluid. Shuts motor off so it doesn't burn up. AFAIK you can't buy any parts. WABCO shut off repair parts quite a while ago. Interestingly when NAV first brought this system out their manual had all that repair info. Good luck. |
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2006 school bus brake problem
