Power Master Cylinder. Doosan G33P-5 Plus

Problem: The temperature of the oil is too hot.

Probable Cause:

1. The viscosity of the oil is wrong.

2. Air mixed with the oil.

3. The relief valve is set too high (priority valve).

4. There is a restriction in the line circuit.

5. Unit being held in relief mode for long periods of time.

Power Master Cylinder

Problem: Low power braking pressure or loss of power braking

Probable Cause:

1. Insufficient pedal stroke.

2. Lines connected to wrong ports.

3. Insufficient brake flow from the first section of control valve due to a stuck brake spool.

4. Relief valve in brake valve damaged.

5. Seals of servo piston in brake valve got damaged.

Problem: Low manual braking pressure or loss of manual braking

Probable Cause:

1. Insufficient pedal stroke.

2. Air in lines.

3. Damaged servo piston seals and sleeve due to contamination.

Problem: Pedal instability

Probable Cause:

1. Air in lines.

2. Damaged a check valve of brake port in the first section of control valve.

3. Damaged a spring of relief valve in brake valve.

4. Damaged a spring for brake spool in the first section of control valve.

Problem: External leakage

Probable Cause:

1. Damaged master piston or seal of master piston.

2. Casting porosity.

3. Fitting or line leakage.

Vehicle System 54 Testing & Adjusting