Electronic Brake Motor

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I am currently working on a 1989 John Deer Safari 40' motor home with a ford 460 power plant. the engine was remove for rebuilding.

Now after reinstalling I am having brake issues with the belt that runs the brake pump breaking during driving.

I have noticed the electronic motor that is somehow tied to the brake pump is not working and can not find any information on wiring, switching or any other operation.

Help...its ready for the road but can't be stopped.

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White Tail, Welcome to FMCA !!!

I have a copy of the chassis service manual for your coach, but it is over 900 pages long. So here is a link to the manual in PDF form if you have enough internet bandwidth to download it.

The real bummer is they do not separate the Different model chassis. Brake system starts at Page 669. There is an early model and a later model listed as ON / VOY (Carburetor) covered on pages 679 and 680 are drawing covering the different brake plumbing used.

I'm not sure what motor you are referring to as no motor is pictured or listed in the manual.


Well, I have to eat my words regarding an electric motor on the John Deere Chassis, Referred to as HYDRO-MAX POWER BRAKE BOOSTER The information on the system starts at page 720 of the manual and covers how the system works.

The Hydro-Max power brake system is composed of a hydraulic-
powered booster (F), mini-master cylinder ( B), reserve
system electric pump motor (I), relay (H), electric
monitor and a warning system.
During system operation, normal flow from the engine driven
hydraulic pump passes through the steering gear, enters the
inlet port (E) of the booster, flows through the poppet valve
and booster then the flow switch © and exits from the retum
port (D) and returns to the reservoir then back to the brake
Force applied to the pedal rod by the vehicle operator activates
the booster. The resulting pressure in the booster applies
a force to the master cylinder.
A pressure regulating valve inside the booster limits the
maximum internal booster pressure developed during a full
Fluid flow through the flow switch "opens the reserve motor
pump electrical circuit during normal operation.

A separate check valve in the motor pump prevents backflow
through the motor pump during normal power applications.
In the event normal fluid flow from the engine driven hydraulic
pump is interrupted, the electric motor pump provides the
power for reserve stops. Upon flow intemption, the integral
flow switch "closes" energizing a power relay, thereby providing
electrical power to the motor pump.
During reserve operation, fluid is retained within the booster
by an inlet port check valve. The motor pump recirculates
fluid within the booster assembly with pressure built on demand
via the poppet valve. The number of applications is
limited only by the electrical capacity of the vehicle.
Manual braking is also available in the event both the power
and reserve systems are inoperative.
Stopping distances and pedal efforts during a manual brake
application are significantly increased. The vehicle should
not be driven except for emergency removal from the roadway.

1. With the engine off, depress the brake pedal. The electric
motor pump should run and the warning lamp should be
2. Start the engine and push the brake pedal several times.
The electric motor pump should not run and the warning
lamp should not be lighted.
3. Stop the engine, check the reservoir and add fluid as

Regarding the broken belt, I would check the check valves that are mentioned to make sure they are not installed backwards putting undue pressure on the hydraulic system.

White Tail, I sent you a private message with a picture of a brake set up that I think you are talking about.


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