MANIFOLD 2090789 - Caterpillar

Illustration 1 g02475946
627H
Illustration 2 g02475948
623H
Illustration 3 g02475949
621HThis module discusses the features and operation of the brake system and the hydraulic fan system. The following wheel tractor scrapers that are covered in this module:
627H
623H
621HThe brake system and the hydraulic fan system have the following main components:
Monitoring system
Piston pump (brake and hydraulic fan)
Pump Control Valve
Control manifold
Brake accumulator
Service brake control
Wheel group
Parking brake
Parking brake solenoid
Piston motor (hydraulic fan)
Oil cooler (brake and hydraulic fan)Monitoring System
The Caterpillar Monitoring System consists of an action alarm, action light, and a monitoring panel. The monitoring screen contains individual alert indicators for each machine system. The Caterpillar Monitoring System provides four warning categories. The first warning category requires only operator awareness. The second warning category needs operator response. The third warning is the 2S category. The 2S category will inform the operator to change the operation techniques because the brakes are hot. The fourth warning category requires immediate shutdown of the machine systems.ReferenceRefer to the Monitoring System Systems Operations for your machine for additional information.Piston Pump Brake and Hydraulic Fan
The pump for the hydraulic fan and brake system is a variable displacement axial piston pump. When the engine is operating, the pump will produce flow in order to satisfy the following demands:
The demand of the brake system
The demand of the hydraulic fan systemThe pump will produce flow until the following conditions are met:
The pressure setting of the pressure compensator is reached.
The brakes and the hydraulic fan are not being operated.Pump Control Valve
The pump control valve is mounted on the piston pump (brake and hydraulic fan). The pump control valve has two functions. The pump control valve uses load sensing to control system pressure. The pump control valve is load sensing. The piston pump (hydraulic fan and brake) will only produce enough oil flow to satisfy the demand of the hydraulic fan and brake system.Control Manifold
The control manifold directs the oil from the brake and the hydraulic fan pump to the brake circuit and to the fan circuit.Brake Accumulator
There are two brake accumulators in the brake system. The brake accumulators maintain brake system pressure when the pump (hydraulic fan and brake) is not supplying oil.Service Brake Control
The service brake control valve for the service brakes provides the proper flow in order to engage the service brakes. The service brake control for the service brakes also balances the oil pressure between the front and rear brakes.Wheel Group
Service Brakes
The service brakes are located in the wheel groups. The service brakes are applied by oil pressure from the service brake control valve. The service brakes are released by retraction springs. The service brakes are activated when the brake pedal is depressed.Parking Brakes
The parking brakes are located in the wheel groups. The parking brakes are applied by springs. The parking brakes are released by oil pressure from the parking brake solenoid.Parking Brake Solenoid
The parking brake solenoid controls the operation of the parking brake. The parking brake is applied when the parking brake solenoid is in the de-energized state. When the parking brake solenoid is energized oil