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0
AM
2020/12/09 Brake System (M0111643-03)
SMCS - 4061, 4250, 4251, 4267, 7000, 7605,
i08217230
7615
PSP-00080508
2025/05/21
01:08:22+08:00
M011164
©32025 Caterpillar Inc.
Illustration 1 g06609749
Schematic standard dry front disc brakes
(1) Secondary brake pressure switch
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(3) Service brake pedal valve
(4) Left front brake group
(5) Front brake cab valve
(6)Accumulator charge valve
(7) Brake filter group / brake filter bypass switch
(8) Brake charge pump/ hoist pump stack
(9) Hydraulic tank
(10)Right front brake group
(11) Brake retract pump/secondary steering pump
(12)To hoist pilot
(13)Tow valve brake
(14)Right rear slack adjuster
(15)Right rear brake group and parking brake
(16) Adapter
(17)Valve Group ARC/TCS
(18)Left rear brake group and parking brake
(19)Left rear slack adjuster
(20) Accumulator parking brake
(21)Brake low-pressure sensor
(22)Brake accumulator
There are two types of braking systems on the machine. One system has dry front disc
brakes consisting of friction material, one friction disc, and two calipers per each
front wheel group (4) and (10) on the machine. When the service brake pedal (3) is
applied, hydraulic pressure causes the front calipers to apply pressure to the friction
material on each side of the friction disc, slowing the machine. The machine also has
wet brakes in side the rear wheel groups. The service brakes are applied by brake oil
pressure that is stored in the service brake accumulator. The brake oil pressure in
the service brake accumulator is developed when the engine is running. The service
brakes are released by spring pressure.
During normal operation, depress service brake control pedal to engage the service
brakes. Use the service brakes for reducing ground speed or for stopping the
machine. The pedal is fully variable. The amount of force that is applied to the
brakes is proportional to the amount of force that is applied to the pedal.
The brake ECM determines whether the service brakes should be engaged for the
function or ARC or TCS.
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Illustration 2 g06609856
Schematic attachment oil cooled front disc brakes
(1) Secondary brake pressure switch
(2) Secondary brake valve /parking brake release
(3) Service brake pedal valve
(4) Left front brake group
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(6)Accumulator charge valve
(7) Front brake slack adjuster /
(8) Brake filter group
(9) brake filter bypass switch
(10)Brake charge pump/ hoist pump stack
(11) Tank
(12)Right front brake group
(13)Brake retract pump/secondary steering pump
(14)Tow valve brake
(15)To hoist pilot
(16)Right rear slack adjuster
(17)Right rear brake group and parking brake
(18) Adapter
(19)Valve Group ARC/TCS
(20)Left rear brake group and parking brake
(21)Left rear slack adjuster
(22) Accumulator parking brake
(23)Brake low-pressure sensor
(24)Brake accumulator
The second version of the braking system consists of wet front brakes. Inside the front
wheel group are two sets of friction plates that are cooled by an oil bath. When
service brake pedal (3) is pressed, hydraulic pressure is distributed to each front
wheel group. Inside the wheel group one set of friction plates are stationary and one
group of plates rotates with the wheel. As pressure is applied, the rotating plates
are pressed against the stationary plates creating friction which forces the wheels to
slow down or to stop.
Accumulators help provide pressure to the braking system as the system is being
engaged and then replenished by a series of valves, sensors, and the brake charge
pump to maintain system pressure.
Secondary Brake Control
To avoid the possibility of a unexpected machine movement
when parking on a slope, always block the wheels securely
before leaving the machine unattended.
If the secondary brake system is required in order to stop the
machine, do not operate the machine until a complete check has
been made of the entire braking system and until all necessary
repairs have been made.
The secondary brake pedal is on the floor of the cab. To modulate the secondary
brakes, the operator presses the secondary brake pedal. Pressing the secondary
brake pedal causes the brake ECM to modulate pressure to the spring-applied brake
pack through use of the secondary brake valve.
Note: The secondary brake system utilizes the parking brake system to apply braking
force to the rear wheels. This system also utilizes the front service brake system to
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If there was failure of the service brakes, depress secondary brake control pedal to
engage the secondary brake system. The amount of force that is applied to the
brakes is proportional to the amount of force that is applied to the pedal.
To obtain the maximum available braking force to the machine in an emergency
stop condition, apply both the service and secondary brake control pedals
simultaneously.
Parking Brake Control
Note: The parking brake is used for parking the truck and is applied by placing the
direction/speed lever in the PARK position. Do not use the retarder levers for parking the
truck.
Parking brake control is performed by the brake ECM. The parking brake is a spring-
applied brake and does not release if hydraulic brake pressure is lost. The parking
brakes are released by brake oil pressure that is stored in the secondary brake
accumulator. The brake oil pressure in the secondary brake accumulator is
developed when the engine is running.
The parking brakes will engage both rear parking brakes when any of the following
conditions are met:
Keyswitch is in the OFF position.
Direction/speed control is in the PARK position.
The brake oil pressure from the secondary brake accumulator is exhausted.
Following is the operation of the parking brake:
1. The operator places the shift lever in PARK position.
2. The brake ECM receives the shift lever position from the transmission ECM.
3. The operator presses the secondary brake pedal.
4. The brake ECM de-energizes the secondary/park brake solenoid.
5. This action engages the rear spring-applied parking brakes.
Parking Brake Indicator - When the
parking brakes are applied, the
parking brake indicator will illuminate.
Manual Retarding Control
Manual retarding is performed with a lever on the steering column. Manual retarding
is performed by energizing the enable solenoid valve and then modulating the left
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Automatic Retarder Control
Automatic retarding is performed when the "ARC" switch kept ON by energizing the
enable solenoid valve and then modulating the left and right proportional solenoid
valves.
Traction Control System
The TCS monitors the drive wheels through four input speed signals: one at each
drive axle and two at the transmission output shaft. Based on the input signals,
Traction control is performed by energizing the enable solenoid valve and then
modulating the proportional solenoid valve for the side that is slipping.
Brake ECM System
The brake electronic control module (ECM) controls the following braking functions:
Service braking
Secondary braking
Park braking
Manual retarding
Automatic retarder control (ARC)
Traction control system (TCS)
The brake ECM also performs monitoring of the system and diagnostic warnings
through the graphical display module.
Note: The parking brakes are spring-applied. The parking brakes are released by
brake oil pressure that is stored in the secondary brake accumulator. The brake oil
pressure in the secondary brake accumulator is developed when the engine is
running.
Diagnostic Capabilities
The ECM also provides enhanced diagnostics. These diagnostics are available by
using onboard memory. Onboard memory stores the diagnostic codes for retrieval
at the time of service. Service personnel can use the Cat® Electronic Technician
(Cat® ET) service tool for troubleshooting.
PSP-00080508
2025/05/21
01:08:03+08:00
i08217230
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AM © 2025 Caterpillar Inc.
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