621H, 623H and 627H Wheel Tractor-Scrapers Hydraulic and Steering System Caterpillar

Introduction

This procedure checks the forward and reverse speeds of the elevator

Perform all tests with the hydraulic oil at the normal operating temperature. Also, make the tests when the tractor engine is at high idle rpm. Use a stopwatch in order to find the times.

If the travel time is not correct, check the following list:

• Check pump efficiency.

• Check the setting of the relief valve for the elevator circuit.

• Check the hydraulic motor.

• Check the adjustment of the elevator chain.

Tools required

Machine Preparation

1. Move the machine to a smooth, horizontal location. Move the machine away from other operating machines and away from personnel. Place the transmission direction control switch in the NEUTRAL position. Engage the parking brake. Lower the bowl to the ground. Retract the ejector cylinder and disengage the cushion hitch. Shut off the engine and turn the engine start switch the ON position. Place chocks in front of the wheels and behind the wheels.

2. Place a mark on one flight of the chain. Operate the engine at High Idle.

3. Warm up the engine to the normal operating temperature.

Perform the Check

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Illustration 1	g02609616

1. Move the elevator switch, that is located on the control joystick to the HIGH SPEED FORWARD position. The time that is required for the chain to make one revolution is 4.65 seconds ± .5 seconds

2. Repeat Step 1 in the HIGH SPEED REVERSE position.