FOOT 0334050 - Caterpillar

Standard Metering Pump
Illustration 1 g02722945
(1) Metering Pump
Illustration 2 g02722976
(1) Metering Pump
(2) Inlet Port
(3) Tank Port
(4) Left Port
(5) Right Port
(6) Load Sense Port The metering pump (1) controls the flow of oil from the steering pump to the steering cylinders. The metering pump is located under the operator platform above the articulation joint. Access to the metering pump is underneath the operator platform.When the steering wheel is not being turned, the control section is in the NEUTRAL position. The metering pump is a closed center valve. The oil grooves in the spool and the oil holes in the sleeve are not aligned in the NEUTRAL position.A small amount of oil flows through the metering pump in the NEUTRAL position. The small flow of oil keeps the spool open slightly. By being open slightly, the metering pump can respond quickly to steering movements. The flow helps keep the spool and sleeve at the same temperature to avoid sticking caused by thermal shock (warm oil hitting a cold HMU).When the steering wheel is turned for a right turn, oil from the steering pump flows into the metering pump through inlet (2). The oil flows from inlet (2) to the gerotor. When the steering wheel is turning, the gerotor is turning and the gerotor is pumping oil. The oil flows from the gerotor through internal passages into the sleeve and into the spool. The holes in the sleeve and the grooves in the spool align. Then, the oil flows to port (5). From port (5), the oil flows to the right steering cylinder.The centering spring is compressed when the spool moves in relation to the sleeve. When you no longer turn the steering wheel, the centering spring will move the spool to the NEUTRAL position. The wheels will stay in position when you stop turning the steering wheel. In order to straighten the machine, you turn the steering wheel to the left.For a right turn, oil flows from the right port to the following locations.
The oil flows to the rod end of the right steering cylinder.
The oil flows to the head end of