990K Wheel Loader Machine Systems Caterpillar

Illustration 1	g03661713
(1) Implement pump (4) Implement pilot filter (5) Implement pilot filter bypass switch (11) Implement pump discharge screen and check valve (38) Implement pump case drain filter (39) implement pump case drain filter bypass switch (47) Implement ECM (57) Key switch (A) Pilot pressure to implement main control valve (B) Implement return line (C) Implement supply

Implement Pump Case Drain Oil Filter

The case drain oil filter removes debris from the hydraulic oil.

During normal operation, oil flows through the oil inlet passages to the oil outlet passages of the filters.

Correct maintenance recommendations must be followed in order to ensure that the filters do not become plugged with debris. If a filter is plugged, the flow of filtered oil to the system stops. However, unfiltered oil will flow past the bypass valve which is located inside the filter housing. When the oil does not flow through the filter element, the debris in the oil may damage components in the hydraulic system.

The filter bypass switch is monitored by the implement ECM. When the filter element is plugged, oil pressure in the filter housing increases. This pressure causes the filter bypass switch to move to the OPEN position.

Hydraulic Oil Filter (Implement Pilot Oil)

The hydraulic oil filter removes debris from the hydraulic oil.

During normal operation, oil flows through the oil inlet passage to the oil outlet passage of the filter.

Correct maintenance recommendations must be followed in order to ensure that the filter does not become plugged with debris. If the filter is plugged, the flow of filtered oil to the system stops. However, unfiltered oil will flow past the bypass valve which is located inside the filter housing. When the oil does not flow through the filter element, the debris in the oil may damage components in the hydraulic system.

The filter bypass switch is monitored by the implement ECM. When the filter element is plugged, oil pressure in the filter housing increases. This pressure causes the filter bypass switch to move to the OPEN position.

The implement ECM will display a Warning Category 2. A Warning Category 2 indicates that the filter has been plugged for more than 30 seconds.

Note: The oil will also bypass the pilot filter element during cold start-up conditions when the oil is below 52 °C (125 °F). In this case, the graphical display will not display a warning. As the oil warms up, the bypass valve will move to the CLOSED position. With the bypass closed, oil flows through the pilot filter element unless the pilot filter element is plugged.

Hydraulic Oil Filter (Implement Discharge Oil)

The hydraulic oil filter removes debris from the hydraulic oil.

During normal operation, oil flows through the oil inlet passage to the oil outlet passage of the filter.

Correct maintenance recommendations must be followed in order to ensure that the filter does not become plugged with debris. If the filter is plugged, the flow of filtered oil to the system stops. However, unfiltered oil will flow past the bypass valve which is located inside the filter housing. When the oil does not flow through the filter element, the debris in the oil may damage components in the hydraulic system.

The filter bypass switch is monitored by the implement ECM. When the filter element is plugged, oil pressure in the filter housing increases. This pressure causes the filter bypass switch to move to the OPEN position.

The implement ECM will display a Warning Category 2. A Warning Category 2 indicates that the filter has been plugged for more than 30 seconds.

Note: The oil will also bypass the pilot filter element during cold start-up conditions when the oil is below 52 °C (125 °F). In this case, the graphical display will not display a warning. As the oil warms up, the bypass valve will move to the CLOSED position. With the bypass closed, oil flows through the pilot filter element unless the pilot filter element is plugged.