D6N Track-Type Tractor Hydraulic System Caterpillar

Introduction

The pressure reducing valve reduces the implement hydraulic pressure. The relief valve prevents excessive pressure buildup in the pilot system. If a high pressure situation occurs, the relief valve will open. Excess pressure is relieved through the valve.

The pressure in the pilot system controls the response of the implements. Low pilot pressure produces poor response in the implement control levers. High pilot pressure produces extreme sensitivity in the implement control levers.

The following test procedure will verify whether the pressure setting for the pilot pressure is within the specified limit. The following adjustment procedure will explain the procedure for adjusting the pilot pressure.

Pilot pressure is controlled by the pressure reducing valve, which is located in the pilot manifold.

Required Tools

Illustration 1	g01291479

Test Procedure (Pressure Reducing Valve)

The pressure reducing valve is located behind an access panel on the right console of the operator station.

Illustration 2	g01072817
Right side view

Illustration 3	g01072843
(1) Accumulator (2) Manifold and reducing valve (3) Pressure reducing valve (4) Relief valve

Illustration 4	g01258208

The pressure tap is located behind an access door on the right fender of the machine.

(5) Pilot supply pressure (pressure after pressure reducing valve)

1. Start the Engine.

2. Attach tetragauge (A) to pressure tap (5) for pilot pressure on the right fender.

3. Operate the engine at HIGH IDLE and exercise the implement hydraulics. The pilot pressure should be a maximum of 3275 ± 175 kPa (475 ± 25 psi).

4. If the pilot pressure is not within the specified limit, perform the steps in "Adjustment Procedure (Pressure Reducing Valve)".

Adjustment Procedure (Pressure Reducing Valve)

1. Remove the operator's seat.

2. Remove the access panel from the right console of the operator station.

3. Loosen the locknut on the adjustment screw of pressure reducing valve (3). Turn the adjustment screw until the pilot pressure is correct.

   Note: One turn adjusts the pilot pressure by 1380 kPa (200 psi).

4. Tighten the locknut on the adjustment screw to a torque of 12 N·m (9 lb ft).

5. Remove the pressure gauge from pressure tap (5) .

6. Install the access panel on the right console of the operator station.

7. Install the operator's seat.