Crankcase Oil Level
Check the level of the oil in the crankcase. Add oil if needed. It is possible for the oil level to be too far below the oil pump supply tube. This will cause the oil pump not to have the ability to supply enough lubrication to the engine components, or to supply enough oil to the high pressure hydraulic pump for proper operation of the unit injectors.
Oil Pump Does Not Work Correctly
The inlet screen of the supply tube for the oil pump can have a restriction. This will cause cavitation (low pressure bubbles suddenly made in liquids by mechanical forces) and a loss of oil pressure. Air leakage in the supply side of the oil pump will also cause cavitation and loss of oil pressure. If the bypass valve for the oil pump is held in the open (unseated) position, the lubrication system cannot get to maximum pressure. Oil pump gears that have too much wear will cause a reduction in oil pressure.
Oil Filter Bypass Valve
If the bypass valve for the oil filter is held in the open position (unseated) because the oil filter has a restriction, a reduction in oil pressure can result. To correct this problem, remove and clean the bypass valve and bypass valve bore. Install a new Caterpillar oil filter to be sure that no more debris makes the bypass valve stay open.
Too Much Clearance At Engine Bearings Or Open Lubrication System (Broken Or Disconnected Oil Line Or Passage)
Components that are worn and have too much bearing clearance can cause oil pressure to be low. Low oil pressure can also be caused by an oil line or oil passage that is open, broken or disconnected.
Piston Cooling Jet Tube
More than one type cooling jet is in use, and they are not interchangeable. Follow the engine arrangement to be sure that correct parts are being installed.
When the engine is operated, cooling jets direct oil toward the bottom of the piston to cool the piston and also provide lubrication for the piston pin. If a cooling jet is broken, plugged or installed wrong, seizure of the piston will be caused in a very short time.