Hydraulic Control Valve. Doosan G33P-5 Plus

Problem: Leakage at the pump shaft seal.

Probable Cause:

1. The shaft seal is worn.

2. There is a broken gasket behind the seal.

3. The inner parts of the pump body are worn.

4. Operation with too low oil level in tank causes suction on the seal.

5. Seal cut on shoulder of pump or keyway during installation.

6. Seal lips are dry and hardened from heat.

Problem: There is a failure pump to deliver the fluid.

Probable Cause:

1. Low level of the oil in the tank.

2. There is a restriction in the pump inlet line.

3. There is air leakage in the pump inlet line.

4. The viscosity of the oil is wrong.

5. The pump has too much wear.

6. Failure of the pump shaft or coupling.

7. The bolts of the pump do not have the correct torque.

8. Filter by-pass not working or installed backwards.

Hydraulic Control Valve

Problem: The control spools do not move freely.

Probable Cause:

1. The temperature of the oil is too high.

2. There is foreign material in the fluid.

3. The fitting connections in the valve body are too tight.

4. The mounting bolts of the valve assembly do not have the correct torque and have twisted the body.

5. Linkage of the lift and tilt levers does not operate smoothly.

6. Bent lift or tilt spools.

7. Damage to the return springs of the spools.

8. The valve is not at normal temperature for operation.

Problem: Control valve spools have leakage around the seal.

Probable Cause:

1. There is some foreign material under the seal.

2. The valve spools are worn.

3. The seal plates are loose.

4. The seals have damage or are badly worn.

Problem: The load lowers when the lift spool is moved from the neutra position to the raise position.

Probable Cause:

1. There is some foreign material in the load check valve area.

2. The load check valve and seat show wear.

3. Sudden loss of pump oil pressure.

4. Damage to the relief valve which causes low oil pressure.

Vehicle System 51 Testing & Adjusting