ROD AS-HYD 0R9234 - Caterpillar

Illustration 1. Location of components in flow control valve.The 4T1008 Valve Group (Charging) will cause higher lifting pressures if it is not operating correctly. This can be caused by either the valve, the signal line orifice, a malfunctioning check valve or shims that have been placed at the bottom of the spring. See Illustration 2.
Illustration 2. Location of components in 4T1008 Valve Group. If hydraulic system overheating occurs on the D6H and D7H Tractors, always use the following checks for correct valve operation before installing a hydraulic oil cooler system.All of these probable causes can be checked by installing a 6V7830 Tetragauge Group in the pump pressure port. Start the machine and allow the hydraulic oil to reach operating temperature. Raise the engine speed to high idle. The pressure on the gauge should be 550 kPa (80 psi) maximum. Lower the engine speed to low idle and then raise it again to high idle. The pressure should be lower at low idle and then return to the original reading at high idle.
Move the dozer lift control approximately 30-35% (towards the "Lift" position) of the lever travel. The pressure should go from 550 kPa (80 psi) to between 2960 kPa (430 psi) and 4000 kPa (580 psi). During this time, the blade should not move. Release the lever to return the valve to the centered position. The pressure should return to below 550 kPa (80 psi). If the pressure does not return to the previous reading or is above 550 kPa (80 psi), the slug in the 4T5006 Valve Group is stuck.
Next, pull the lift control lever fully back. The reading on the gauge should be approximately 9000 kPa (1300 psi) as the standard dozer blade is being raised. (The pressure for plated or heavier dozer blades will be slightly higher.)
If the pressure required to lift the dozer blade is higher, install a pressure gauge in the head end hydraulic line of the lift cylinder. Pull the lift control lever all the way back. If the head end pressure exceeds 690 kPa (100 psi) while lifting the blade, the charging valve is not operating correctly and should be checked.