SLEEVE 6V4129 - Caterpillar

Illustration 1 g00724177
Parking brake air control valveThe parking brake air control valve is located in the control console near the transmission control. The parking brake air control valve controls air flow to the parking and secondary brake valve.
Illustration 2 g00446883
(1) Plunger (2) Lever (3) Passage in plunger (4) Exhaust passage (5) Delivery passage (6) Spring (7) Inlet valve (8) Valve seat (9) Spring (10) Supply passageWhen lever (2) is in the OFF position, lever (2) pushes down on plunger (1). Plunger (1) moves inlet valve (7) off valve seat (8). Plunger (1) also blocks exhaust passage (4). Air pressure from supply passage (10) flows around inlet valve (7) to delivery passage (5) .Air flows out of delivery passage (5) to the parking and secondary brake valve. The air flow pushes down a spool in the parking and secondary brake valve. This allows oil flow to release the spring applied parking brakes for the rear wheels.When lever (2) is moved to the ON position, lever (2) releases plunger (1). Spring (6) raises plunger (1) off inlet valve (7). Spring (9) pushes inlet valve (7) against valve seat (8). The air flow from supply passage (10) is blocked. Delivery passage (5) remains open. The air from the parking and secondary brake valve flows through passage (3) in plunger (1). This air exits the parking brake air control valve through exhaust passage (4) .When air supply to the parking and secondary brake valve is shut off, a spring in the parking and secondary brake valve moves the spool. This stops the oil flow to the chamber for the parking brakes for the rear wheels. The parking brakes for the rear wheels will now engage.