D250E Series II and D300E Series II Articulated Trucks Steering, Suspension, and Body Hoist Hydraulic Systems Caterpillar

Test

The following test will determine if the lower pressure is being regulated properly by the relief valve.

Illustration 1	g00634166
Location of the hoist control valve

Illustration 2	g00497454
The hoist control valve is located on the rear of the front frame. The guard has been removed for photographic clarity. (1) Lower relief valve (2) Lower pressure port

1. Stop the engine and make sure that the hydraulic oil is at normal operating temperature. Install the steering frame locks.

2. Install a 0 to 28000 kPa (0 to 4000 psi) pressure gauge on the lower pressure test port (2) .

3. Start the engine and run the engine at low idle. Lower the dump body into the frame and hold the hoist control lever in the lower position. The pressure gauge should read 6900 ± 140 kPa (1000 ± 20 psi).

4. Stop the engine. Remove the test equipment and remove the steering frame locks.

Adjust

It is possible to adjust the lower relief valve. The following procedure will set the relief pressure.

Illustration 3	g00634166
Location of the hoist control valve

Illustration 4	g00497454
The hoist control valve is located on the rear of the front frame. The guard has been removed for photographic clarity. (1) Lower relief valve (2) Lower pressure port

1. Stop the engine and make sure that the hydraulic oil is at normal operating temperature. Install the steering frame locks.

2. Install a 0 to 28000 kPa (0 to 4000 psi) pressure gauge on the lower pressure test port (2) .

3. Loosen the jam nut of relief valve (1) .

4. Turn the adjustment screw in the clockwise direction in order to raise the pressure setting. Turn the adjustment screw in the counterclockwise direction in order to lower the pressure setting. One turn of the adjustment screw is equal to approximately 2750 kPa (400 psi). Start the engine and run the engine at low idle. Lower the dump body into the frame and hold the hoist control lever in the lower position. Note the pressure reading at the lower pressure test port (2). The pressure should be 6900 ± 140 kPa (1000 ± 20 psi). Do not turn the adjustment screw more than 1/4 turn at a time. Repeat this procedure until the correct pressure setting is achieved.

5. Tighten the jam nut of relief valve (1) .

6. Stop the engine. Remove the test equipment and remove the steering frame locks.