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Old 02-23-2020, 04:17 PM   #1
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Join Date: Feb 2020
Location: Toronto, ON Canada
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Brake assist continues to run after engine is shut off

Hello everyone, I just joined Skoolie because I've just been handed the fleet manager job. Perhaps it's karma for complaining about the state of repairs of the buses
We have a 2004 International T444E school bus with their engine.
After turning off the engine and removing the key, the brake assist pump continues to run and drains the battery.
Pumping the brake pedal a few times stops the noise and I can only assume this action also turns off the pump.
I'm thinking - hoping - it could be a sticky solenoid or switch?
Any suggestions where to look?
Thanks.

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Old 02-23-2020, 04:26 PM   #2
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PM cowlitzcoach with that one.
he has managed school bus fleets.
but it sounds like an electronic valve failing
dang computer mess
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Old 02-23-2020, 05:50 PM   #3
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Engine: T444E
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Check your brake light switch. Are the brake lights remaining on when the engine is shut down? As I understand it, from a technical perspective, when the brake lights are on and there is no hydraulic pressure (detected), this activates the assist pump.
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Old 02-23-2020, 08:12 PM   #4
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I had the same thing happen with mine. It turned out to be a leaking brake line going to the rear brakes.
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Old 03-22-2020, 01:37 PM   #5
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Turns out I was kinda right. I hope the image I pasted is visible.

It was the solenoid that activates the brake assist motor, taking its cue from the pressure sensor on the side of the master cylinder.
The sensor seemed to be okay.
For some reason I decided to squeeze the top and bottom of the solenoid and the motor shut-off. Pull the pieces apart ever so gently and it activated.
I concluded that the contacts inside are not making properly.
Makes sense, I suppose - if it isn't getting a pressure OK from the sensor, it'll turn on. Equivalent to the contacts not making.
I pulled it apart, cleaned the contacts, put it back together and tightened it with a cable tie. No more problems.
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Old 03-22-2020, 01:49 PM   #6
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Turns out I was pretty close.

I thought it might be centered around the master cylinder since the brake assist motor will run if you press the brake pedal, even with the engine off.
That's when I noticed the large solenoid control module next to the MC, and the pressure sensor coming from the side.
For some reason, I decided to squeeze the top and bottom of the control module and the brake assist shut off.
I gently pried it apart just a bit, and the motor came on again.
It all made sense. If the MC sensor detects low pressure, it signals for brakes assist - exactly the same as if one of the contacts is not making properly in the control module.
So I pulled it apart, cleaned the contacts and tightened the 2 parts with a cable tie and the problem is gone.
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Old 03-23-2020, 01:57 AM   #7
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Join Date: Sep 2015
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This forum may also be useful to you. It is for folks like you that maintain a fleet:


https://www.schoolbusfleet.com/forum/
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