HOSE AS 8W7637 - Caterpillar

Illustration 1 g03590040
(1) Rear service brakes
(2) Wires to transmission electronic control module
(3) Left brake pedal
(4) Wires to stop lamps
(6) Service brake control valve
(7) Accumulator for the front service brakes
(8) Accumulator for the rear service brakes
(9) Parking brake control valve
(10) Parking brake
(11) Parking brake actuator
(12) Parking brake pressure sensor
(13) Front service brakes
(14) Brake oil pressure sensor
(15) Control manifold
(16) Hydraulic oil filter
(17) Piston pump
(18) Breather
(19) Hydraulic oil tank
Illustration 2 g03558937
(DD) Parking brake switch
(EE) Park brake pressure sensor
(FF) Right Pedal position sensor
(GG) Park brake solenoid
(HH) Brake charging solenoid
(JJ) Left pedal sensor
(KK) Brake accumulator pressure sensor
(MM) Brake accumulator pressure sensor Piston pump (17) supplies the hydraulic oil that is required in order to operate the brake and the hydraulic fan system. Oil flows from pump (17) to control manifold (15). The control manifold controls the flow of oil from pump (17) to brake accumulators (7, 8) and piston motor for the hydraulic fan. Control manifold (15) also directs some of the oil to the pilot circuit for the implement and steering systems. A pump control valve limits the oil pressure that flows from pump (17). A pressure relief valve in control manifold (15) acts as a backup to the pump control valve.Control manifold (15) contains a priority valve and a cut-in/cut-out valve. The priority valve is a proportional valve. Proportional valves do not shift all the way to a particular position. The valve prioritizes the position that the shift is toward. When the cut-in/cut-out valve is shifted to the left, the priority valve is shifted to the right. With the priority valve shifted to the right, oil flows to an inverse shuttle valve that is located in control manifold (15). The oil then flows to brake accumulators (7, 8). When the accumulators are charged, the cut-in/cut-out valve shifts to the right, and the priority valve shifts to the left. Oil then flows to the fan circuit. The oil flows through a pressure reducing valve. From the pressure reducing valve, the oil flows to piston motor for the hydraulic fan system. A port in control manifold (15) connects to brake oil pressure sensor (14). Brake oil pressure sensor (14) monitors the oil pressure in the brake accumulators. If the oil pressure in either brake accumulator drops below the minimum threshold, sensor (14) sends a signal to the power train ECM. The power train ECM will cause a warning to sound in the cab.Brake accumulators (7, 8) contain a precharge of dry nitrogen. When oil flows into an accumulator, the pressure oil moves the piston inside the accumulator. The piston moves against the charge of dry nitrogen gas. This piston pushes the dry nitrogen until the oil pressure reaches the cut out pressure. The oil also flows to service brake control valve (6).Service brake control valve (6) is in the circuit from the accumulators to the service brakes. When the left brake pedal is pushed, oil from each accumulator flows to the service brakes. The service brakes are then applied.When service brake control valve (6) is