SCREW-HEX SKT 4983393 - Caterpillar

Introduction
The issue that is identified below does have a known permanent solution. Use the solution that is identified below.Problem
A high-pitched noise can be produced by the load sensing line for the implement pump when the implement pump is at high-pressure standby. This process happens when maximum pressure and minimum flow are requested. Such as, continuing to command a hydraulic function after hitting the stops or reaching full cylinder extension or retraction. A common example is continuing to command the "TILT BACK" function after the bucket has contacted the rack stops. This process is caused by an instability in the load sensing line at high-pressure standby. This instability does not damage the pump or the hydraulic system.Solution
Stop the hydraulic function after hitting the stop or reaching full cylinder extension or retraction. This procedure will eliminate the noise. Activation of another hydraulic function will cause the implement pump to upstroke. This procedure will also eliminate the noise.In some cases, noise is caused by a hydraulic line in contact with the bottom of the cab. This contact will conduct hydraulic noise into the cab. This issue is normal hydraulic noise that is not related to the instability at high-pressure standby. Ensure that no hydraulic lines are in contact with the bottom of the cab.