D330, D333, 3304, 3306 – Low Oil Pressure

Oil Pressure Gauge
A defective oil pressure gauge may show low oil pressure.

Crankcase Lubricant Level
Oil level can be too low for oil pump suction bell pickup. Check oil level and add if necessary.

Pump Malfunctions
The oil pump inlet screen can be restricting the suction side of the pump which results in cavitation and loss of oil pressure. An air leak in the suction side of the pump will also cause cavitation and loss of pressure. An oil pump bypass valve that is stuck in the open (unseated) position will not allow system pressure to build to maximum pressures. The oil pump gears can be worn sufficiently to cause a reduction in pump output.

Oil Filter and Bypass Valve
If the oil filter is restricted and the filter bypass valve (end of filter housing) is stuck in the closed position, oil pressure may be low. Install a new Caterpillar oil filter element, disassemble the bypass valve, clean the spring and plunger. Be sure the plunger moves freely in the valve before assembling the bypass valve.

Excessive Clearance in Engine Bearings or Open System
Worn components with extreme bearing clearances can cause engine oil pressure to be abnormally low. Any open, broken, or disconnected oil lines or passages will cause loss of oil pressure. Check gallery and crankshaft plugs to be sure they are in place.

Oil Cooler and Bypass Valve
Check the oil cooler oil passages for sludge. A clogged oil cooler with a stuck cooler bypass valve will be accompanied by high engine operating oil temperatures. Oil pressure will usually not lower due to sludge deposits alone. The cooler bypass valve must be stuck closed, or nearly so, to lower the oil pressure.

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