651E and 657E Wheel Tractor-Scrapers Hydraulic System Caterpillar

The hydraulic cylinder drift is the movement of the cylinder rod. The cylinder rod is either moving in or moving out of the cylinder. During normal machine operation, movement of the cylinder rod will have an effect on the performance of the machine.

Any of the following examples may cause cylinder drift:

• The seal on the cylinder piston is damaged.

• A scratch or a groove is in the cylinder bore.

• A scratch or a groove is on the cylinder rod.

• The seal in the cylinder head is damaged.

• Loose fittings or damaged hydraulic lines have oil leaks.

• Dirt in the main relief valve or the main relief valve is damaged.

Before you begin the following procedure, refer to Testing and Adjusting, "Machine Preparation for Troubleshooting".

Drift of Bowl Cylinders

Illustration 1	g00693205
Location of Marks for Drift of Bowl Cylinder (1) Second mark (2) First mark (3) Measurement

1. Start the engine. Operate the machine until the hydraulic oil reaches normal operating temperature.

2. Stop the machine on a hard, level surface. Run the engine at LOW IDLE in NEUTRAL.

3. Raise the bowl within 100 mm (3.9 inch) of full retraction.

4. As shown, put mark (2) along the draft arm on the side of the bowl.

5. As shown, put mark (1) along the draft arm on the side of the bowl after five minutes.

6. Record measurement (3). Measurement (3) should not exceed 8 mm (0.3 inch).

7. Lower the bowl. Stop the engine.