ACCUMULATOR GP-HYDRAULIC 3178429 - Caterpillar

Sudden movement of the machine or release of oil under pressure can cause injury to persons on or near the machine.To prevent possible injury, perform the procedure that follows before testing and adjusting the brake system.
Personal injury can result from hydraulic oil pressure and hot oil.Hydraulic oil pressure can remain in the hydraulic system after the engine has been stopped. Serious injury can be caused if this pressure is not released before any service is done on the hydraulic system.Make sure all of the attachments have been lowered, oil is cool before removing any components or lines. Remove the oil filler cap only when the engine is stopped, and the filler cap is cool enough to touch with your bare hand.
Note: If the machine is equipped with a brush cutter, refer to Operations and Maintenance Manual, "Jumper Hose Installation (Brush Cutter)".This test checks the cut-in pressure, the cut out pressure, the nitrogen precharge, and the pressure switch that indicates low oil pressure.
Table 1
Required Tools    
Part Number     Description     Qty    
198-4240     Digital Pressure Indicator     1    
Stop the engine. Engage the parking brake. Depress the brake pedal at least fifty times until there is no brake oil pressure. Pause for two seconds between each of the applications.
Illustration 1 g00488877
(1) Pressure tap (2) Accumulator manifold
Install 198-4240 Digital Pressure Indicator to pressure tap (1) that is on accumulator manifold (2) .
Observe the pressure gauge. Before you start the engine, the oil pressure must be 0 kPa (0 psi).
Start the engine. The oil pressure will increase to a maximum. Record this pressure. This is the cut out pressure of the brake accumulator charging valve. The correct cut out pressure should be 13100 kPa (1900 psi).
Apply the service brakes repeatedly while the engine is running. Verify that the pressure drops consistently. Record the point, when the pressure begins to increase quickly. This is the cut-in pressure. The cut-in pressure should be 6900 1500 kPa (1000 220 psi).
Stop the engine. Depress the brake pedal until the pressure gauge decreases to 5170 170 kPa (750 25 psi). The warning light on the dash for the low oil pressure should turn ON. If this does not occur replace the pressure switch.
Continue depressing the brake pedals after the warning light for low oil pressure turns ON. Watch for a rapid decrease in the oil pressure. Record the pressure, when the pressure decreases rapidly. This is the approximate nitrogen precharge pressure in the brake accumulator. If the nitrogen precharge pressure is not within the specification, refer to Testing and Adjusting, "Brake Accumulator - Test and Charge".
If the cut-in pressure and the cut out pressure are not within the specification, stop the engine and completely release all oil pressure from the brake circuit by depressing the brake pedal at least fifty times. Loosen the hydraulic tank filler cap in order to make sure that there is no residual pressure in the hydraulic tank. Replace the steering and