SUPPORT 2226449 - Caterpillar

Introduction
The following procedure is designed to check the pressure for the front brake manifold. The pressure comes from a pressure reducing valve on the pilot/differential manifold that is located under the cab. This pressure is used to supply all the functions that are on the manifold. These functions include the service brakes, the front differential lock, and the parking brake.Required Tools
Table 2
Required Tools    
Item     Description    
AA    
34475 kPa (5000 psi) pressure gauge    Machine Preparation
Prepare machine for troubleshooting.ReferenceFor more information on preparing the machine for troubleshooting, refer to the Service Manual module for the power train Testing and Adjusting, "Machine Preparation for Troubleshooting" for the machine that is being serviced.
Illustration 1 g03636016
Illustration 2 g03638159
Location of the accumulator
Raise the cab to gain access to the brake accumulator. Refer to the Operation and Maintenance Manual for instructions to raise the cab.
Illustration 3 g03638251
(!) Brake accumulator (2) accumulator drain valve
Illustration 4 g03647661
Close view of accumulator drain valve
Open the brake accumulator drain valve. This action will drain the oil out of the accumulator. Close the brake accumulator drain valve.Test Procedure Front Brake Manifold
The test procedure requires two people to perform the test.
Illustration 5 g03635321
Illustration 6 g03635420
View from the front of the machine looking towards the cab
Remove the cover from the front frame.
Illustration 7 g03638297
Location of Pressure Tap (1) Pressure tap for the front brake manifold.Note: The pressure tap for the front brake is located on the front manifold.
Remove the protective cap from pressure tap (1) in order to test the oil pressure of the front brake. Connect the 34475 kPa (5000 psi) pressure gauge (AA) .
Look at the pressure gauge. Before the engine is started, the oil pressure must be 0 kPa (0 psi).
Close the cab door.
Illustration 8 g03601696
Start the engine and allow the hydraulic oil to reach normal operating temperature. Press arming button to activate the machine functions.
Read the pressure on gauge (AA) and compare to the desired pressure of 11030 kPa (1600 psi).
If the front brake manifold pressure is not correct, follow the procedure to adjust the pressure reducing valve on the pilot differential manifold. If the pressure is correct, shut off the machine. Remove the pressure gauge. Install the cover.Adjust Procedure for Pressure Reducing Valve
Leave the pressure gauge hooked up.
Tilt the cab to access the pressure reducing valve on the pilot differential manifold.
Illustration 9 g03638308
(3) Pressure reducing valve
Unlock the set screw on pressure reducing valve (3). Turn in to increase pressure, turn out to decrease pressure. Set the pressure to 11032 kPa (1600 psi). Tighten the locknut on pressure reducing valve (3) .
Shut the engine off. Lower the cab. Remove the gauge. Install the cover.