881879T26 Mercury SENSOR, Pressure, Water Pressure

An oil pressure gauge that has a defect can give an indication of low oil pressure or high oil pressure.
Illustration 1 g00284796
1U-5470 Engine Pressure Group
(1) Pressure indicators
(2) Zero adjustment screw
(3) Pressure indicator
(4) Pressure tap
(5) Pressure indicator The 1U-5470 Engine Pressure Group can be used in order to measure the pressure in the system. This tool group has a gauge in order to read pressure in the oil manifold. For more information, refer to Special Instruction, SEHS8524.Cat ET can also be used to measure the oil pressure in the system.
Illustration 2 g00322890
Oil gallery plug (typical example)
(6) Oil gallery plug
Work carefully around an engine that is running. Engine parts that are hot, or parts that are moving, can cause personal injury.
Oil pressure to the camshaft and main bearings should be checked on each side of the cylinder block at the oil gallery plug (6). With the engine at operating temperature, the minimum oil pressure at full load rpm should be approximately 280 kPa (40 psi). Minimum oil pressure at low idle rpm should be approximately 140 kPa (20 psi).Indicators For Oil Pressure
An oil pressure indicator that has a defect or a sender that has a defect can give an indication of a low oil pressure or a high oil pressure.The 1U-5470 Engine Pressure Group or the Cat ET service tool can be used in order to make a comparison with the engine oil pressure gauge on the instrument panel.Oil Pressure Is Low
Crankcase Oil Level
Check the level of the oil in the crankcase. Add oil if oil is 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.The Oil Pump Does Not Work Correctly
The inlet screen of the supply tube for the oil pump can have a restriction. This restriction will cause cavitation 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 position, the lubrication system can not reach the 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 one or more of the oil filters is held in the open position due to a restriction, a reduction in the oil pressure can be the result. Remove each bypass valve and clean each bypass valve in order to correct this problem. You must also clean each bypass valve bore. Install new Caterpillar oil filters. New filters will prevent more debris from causing this problem.Too Much Clearance At Engine Bearings Or Open Lubrication System
Components that are worn and components that have too much bearing clearance can cause low oil pressure. Low oil pressure can also be caused by an oil line or an oil passage that is open, broken, or disconnected.Piston Cooling Jets
When the engine is operating, piston cooling jets direct oil toward the bottom of the piston in order to cool the piston. This also provides lubrication for the piston pin. If a jet is broken, plugged, or installed incorrectly, a seizure of the piston will occur quickly.Oil Pressure Is High
Oil pressure will be high if the bypass valve for the oil pump can not move from the closed position.