ENGINE AR-REPL 4742660 - Caterpillar

Air Cylinders
Rear Of Engine
(1) Air cylinder for rear wheel brakes. (2) Master cylinder for rear wheel brakes. (3) Air cylinder for front wheel brakes. (4) Master cylinder for front wheel brakes (general location). (5) Brake fluid pressure (overstroke) switches.The two air cylinders are part of the air/hydraulic cylinders. Air cylinders (1) and (3) are under the hood at the rear of the engine.The air cylinder changes the energy of air under pressure into force and movement needed for brake application. The ratio of air pressure to brake fluid pressure is 1 to 16. [If the pressure at air inlet (10) is 70 kPa (10 psi), the pressure in the master cylinder (11) is 1100 kPa (160 psi).]
Air Cylinder (With Brakes Activated)
(5) Brake fluid pressure (overstroke) switch. (6) Piston. (7) Rod. (8) Spring. (9) Indicator rod. (10) Air inlet. (11) Master cylinder.When a brake pedal is pushed down, air under pressure goes from the brake control valve to inlet (10) of the air cylinder and pushes on piston (6). Piston (6) pushes on rod (7), which pushes on a piston in master cylinder (11). The end of rod (7) is held by the piston in the master cylinder.
Air Cylinder (With Brakes Released)
(5) Brake fluid pressure (overstroke) switch. (6) Piston. (7) Rod. (8) Spring. (9) Indicator rod. (10) Air inlet. (11) Master cylinder.When the brakes are released, spring (8) returns the piston, rod and master cylinder piston to their original positions.If piston (6) comes in contact with indicator rod (9), rod (9) will move and open switch (5). This will cause the EMS brake fluid pressure indicator to FLASH. If this does happen, there is a problem in the hydraulic circuit for the wheel brakes. See the Testing and Adjusting section on HOT OR DRAGGING BRAKES. After piston (6) comes in contact with indicator rod (9), the rod must be manually pushed back into the air cylinder to its original position.Hydraulic Circuit For The Wheel Brakes
Hydraulic Circuit
(1) Air/hydraulic cylinders (two). (2) Brake fluid pressure (overstroke) switches (two). (3) Air lines (two) from double check valve. (4) Brake fluid reservoirs (two). (5) Breathers (two). (6) Brake fluid pressure indicator. (7) Fault alarm. (8) Wheel brakes (four).The hydraulic circuit is divided into two separate circuits, one for the front wheel brakes and one for the rear wheel brakes. Each circuit has a reservoir, an air/hydraulic cylinder and two wheel brakes.Air/hydraulic cylinders (1) have two pistons each, one for air (air cylinder) and one for brake fluid (master cylinder). The air cylinders are part of the air circuit for the wheel brakes. Air pressure in the air cylinders moves the piston in the master cylinders, which causes the compression of the brake fluid in the hydraulic circuit and activates the brakes.Reservoirs (4) provide extra brake fluid for the master cylinders.Wheel brakes (8) are at all four wheels. They are used to stop the movement of the machine during normal operation.Brake fluid pressure (overstroke) switches (2) activate brake fluid pressure indicator (6) when there