BOWL A 8T5124 - Caterpillar

Illustration 2. Cylinder Drift = Distance A - Distance B. The drift distances are for new machines. Tilt Cylinder Drift Test
1. Lift the bucket to the maximum height, and move the control lever to the "Hold" position.2. Activate the tilt circuit until the bucket is at the angle to dig (almost level).3. Place a mark on the tilt cylinder for drift measurements (see Lift Cylinder Drift Test).4. Measure the distance A minus B (and check the time) that the cylinders retract with Chart B. If the drift is "Not" within Caterpillar specification, continue to the appropriate section(s) that follow.
1. Troubleshooting The Lift Cylinder2. Troubleshooting The Tilt CylinderTroubleshooting The Lift Cylinder
Fluid Spillage Containment
Care must be taken toensure that fluids are contained during performance of inspection, maintenance, testing, adjusting and repair of the machine. Be prepared to collect the fluid with suitable containers before opening any compartment or disassembling any component containing fluids. Refer to "Tool And Shop Products Guide", NENG2500 for tools and supplies suitable to collect and contain fluids in Caterpillar machines. Dispose fluids according to local regulations and mandates.
Contamination Of The Shuttle Valve
One of the most prevalent causes for excessive lift cylinder drift is a contaminated shuttle valve. This condition provides an open line between the head and rod ends of the cylinders.
If the driftbecomes increasingly apparent over time, first check the shuttle valve for contamination and integrity. If contamination is found, clean or replace the shuttle valve (except in the 938F, 980F and 980F Series II Wheel Loaders listed, which use check valves) and replace and inspect the hydraulic oil filter(s).
Pilot Valve
The pilot valve can contribute to drift while in the "Hold" position if not correctly adjusted or if internal leakage is present. To reduce drift due to the pilot valve, use the following procedure.
1. Raise the bucket in the same manner as performing the drift test.2. With the engine on, engage the Hydraulic Lockout.If the drift is reduced, the problem could be one of the following:
a. Pilot pressure is being provided to the control valve while in the "Hold" position. If this is the case, check the pilot pressure at the control valve. There should be "0" pressure at each end of the main control lift spool to maintain a correctly centered spool in neutral.b. Internal leakage through the pilot valve. The pilot valve may not be within Caterpillar specification. If this is the case, repair or replace the valve.Refer to the Specifications section of the appropriate Service Manual for pivot plate adjustment.Pressure Control And Selector Valve
If the drift rate is higher at low idle than at high idle, check for cylinder bleed back through the dead engine pilot supply in the selector valve.
1. Disconnect and plug the pressure line coming from either the manifold or the ride control valve at the cylinder port on the pressure control and selector valve. If the drift is reduced, check the selector valve spool for burrs.Otherwise, reconnect the high pressure line and continue with Step 2.
2. Check the