OPERATIONAL PERFORMANCE TEST / Component Test PRIMARY PILOT PRESSURE (Including Brake Circuit) CAUTION: If air is mixed in the brake system, the brake function is reduced, and serious hazard may occur. Bleed air from the brake system after removing and installing the brake piping, and replacing hydraulic oil. Refer to Troubleshooting B in Group T5-6. IMPORTANT: When pressure in the service brake accumulator lowers, the primary pilot pressure circuit flows pressure oil from the pilot pump to the brake cir- cuit and accumulates pressure in the accumulator. Therefore, pressure on the brake circuit is 15 MPa (153 kgf/cm 2 , 2180 psi) or higher and is higher than pressure in the pilot cir- cuit.
Use a pressure gauge capable of measuring 15 MPa (153 kgf/cm 2 , 2180 psi) or higher. Preparation: 1. Stop the engine. 2. Push the air bleed valve of the hydraulic oil tank and release any remaining pressure. 3. Disconnect the hose from the pilot filter inlet or outlet port. Install adapter (13/16-16UNF), a nipple, a pressure gauge and a coupling between the pilot filter and the hose. Hose (3/4-16UNF) Pilot Filter T4GB-04-05-001 : 22 mm, 24 mm, 27 mm 4. Start the engine. Check for any oil leaks at the pressure gauge connection. 5. Maintain hydraulic oil temperature at 50 ± 5 ° C (122 ± 9 ° F). Measurement: 1. Set engine speed at fast idle. Depress the accel- erator pedal fully. 2.
Measure pilot pressure without load by using a pressure gauge. 3. Repeat the measurement three times and calcu- late the average values. Evaluation: Refer to the Performance Standard Table in Group T4-2. T1F3-04-05-001 NOTE: When pressure in the service brake accu- mulator lowers during measurement of pri- mary pilot pressure, the measured valve is increased to 15 MPa (153 kgf/cm 2 , 2180 psi) for several seconds. T4-5-1