# International 4700 power brake question.



## Hoodoo Valley (Nov 14, 2006)

I've got an International 4700 and it's been sitting awhile. I started it up to make sure it runs, circulate the fluids and charge the batteries. I ran it through the gears and everything checks, but when I press the brake pedal, you can hear an electric motor running to boost the braking effort, but it continues running as long as my foot is on the brake pedal. Don't recall if it typically did that or if it ran a bit then stopped once the pressure built up. The question: Should the power assist motor run as long as the brake pedal is depressed, or should I be looking into something needing attention?


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## Hoodoo Valley (Nov 14, 2006)

Oh, and the brake fluid appeared to be up to the proper level, but I couldn't readily see any marks in the reservoir standing on the ground. Master cylinder sits up fairly high....


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## Ed Williams (Jun 13, 2019)

I am not familiar with the 4700, but my father in law has a BIG dump converted to a manure spreader. His brakes are air assist with a pressurized air tank. The electric compressor operates like a home compressor with an adjustable pressure switch that kicks the electric compressor on and off as needed. Constant running of the compressor indicates an air leak which must be corrected before the brakes lock up. It took me a while to understand that the air keeps the shoes off the drums and not the other way around. No air means brake shoes are locked to the drum. I don't really understand how the brake pedal regulates the air pressure and braking force. We were only repairing leaks on the air lines to the brakes.


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## Hoodoo Valley (Nov 14, 2006)

This here set up is actually hydraulic and the electric motor sounds like an electric can opener. I push the pedal down at start up and you can hear the electric motor kick in and it seems to run a bit then shut off, but if I really push on the brake, the motor runs constantly and you can feel a pulsing in the pedal. I drove it from Hermiston Oregon to my home, about 300 miles and I really don't recall the motor running when I applied the brakes, but it would have been hard to tell over the engine and road noise really.


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## Hoodoo Valley (Nov 14, 2006)

Bottom line is that there is no lights (on the dash, and there is a brake light indicator to alert the operator to brake issues) and the brakes DO actually work so maybe not an issue?


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## Ed Williams (Jun 13, 2019)

Hoodoo Valley said:


> This here set up is actually hydraulic and the electric motor sounds like an electric can opener. I push the pedal down at start up and you can hear the electric motor kick in and it seems to run a bit then shut off, but if I really push on the brake, the motor runs constantly and you can feel a pulsing in the pedal. I drove it from Hermiston Oregon to my home, about 300 miles and I really don't recall the motor running when I applied the brakes, but it would have been hard to tell over the engine and road noise really.


By your description, it sounds like the electric is a hydraulic assist and the motor would run during braking to provide additional braking force, then shut off when the brake pedal is released. A lot of industrial hydraulic systems are designed in a similar way. There would be a pressure monitoring switch that energizes the motor when the pressure drops below a set point, then shuts off when the set point is achieved. During braking, the pressure in the system would drop, energizing the motor. Depending on how much brake is applied and the duration of the braking, the motor may cycle on and off during one braking incident, but definitely be off during idle braking time. I have designed 35 industrial hydraulic systems all over the the southeast, and this control method is simple, reliable, effective, and almost maintenance free. I think you will find your system is a varient of this type of control system.


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## Ed Williams (Jun 13, 2019)

Hoodoo Valley said:


> Bottom line is that there is no lights (on the dash, and there is a brake light indicator to alert the operator to brake issues) and the brakes DO actually work so maybe not an issue?


I am really surprised that you don't have an idiot light on the dash based on the pressure switch set point. That is a minimum. A pressure gauge on the brake hydraulic system would be better. Do you have to go to the shop and have the codes read to know if the system has a fault? Seems strange. As my Daddy used to say, "IF It Ain't Broke, Don't Fix It", sound advice.


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## Hoodoo Valley (Nov 14, 2006)

That's it exactly. I've read on line that there is an indicator, though I've never seen it lit up.


Ed Williams said:


> By your description, it sounds like the electric is a hydraulic assist and the motor would run during braking to provide additional braking force, then shut off when the brake pedal is released. A lot of industrial hydraulic systems are designed in a similar way. There would be a pressure monitoring switch that energizes the motor when the pressure drops below a set point, then shuts off when the set point is achieved. During braking, the pressure in the system would drop, energizing the motor. Depending on how much brake is applied and the duration of the braking, the motor may cycle on and off during one braking incident, but definitely be off during idle braking time. I have designed 35 industrial hydraulic systems all over the the southeast, and this control method is simple, reliable, effective, and almost maintenance free. I think you will find your system is a varient of this type of control system.


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## Ed Williams (Jun 13, 2019)

Leave well enough alone til something goes wrong. Got back to the constant tractor repair issues.


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## Hoodoo Valley (Nov 14, 2006)

I'm thinking you're right. Moving on to other things..... like sleep right now!


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