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Oil Filter Bypass Valve
If the bypass valve for the oil filters is held in the
open position (unseated) because the oil filters have a
restriction, a reduction in oil pressure can result.  To
correct this problem, remove and clean the bypass valve
and bypass valve bore. Install new Caterpillar oil filters
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
6. Plug.
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.
Work carefully around an engine that is running.
Piston Cooling Jets
Engine parts that are hot, or parts that are moving,
can cause personal injury.
When engine is operated, cooling jets direct oil
toward the bottom of the piston to lower piston and ring
temperatures.  If a jet is broken, plugged or installed
Oil pressure to the camshaft and main bearings
wrong, seizure of the piston will be caused in a very short
should be checked on each side of the cylinder block at
oil gallery plug (6).  With the engine at operating
temperature, minimum oil pressure at full load rpm
should be approximately 280 kPa (40 psi), and minimum
oil pressure at low idle rpm should be approximately 140
Oil pressure will be high if the bypass valve for
kPa (20 psi).
the oil pump can not move from the closed position.
Crankcase Oil Level
When some components of the engine show
bearing wear in a short time, the cause can be a
Check the level of the oil in the crankcase. Add
restriction in an oil passage.
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
If the gauge for oil pressure shows enough oil
pump not to have the ability to supply enough lubrication
pressure, but a component is worn because it can not
to the engine components.
get enough lubrication, look at the passage for oil supply
to the component. A restriction in a supply passage will
Oil Pump Does Not Work Correctly
not let enough lubrication get to a component, and this
will cause early wear.
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
Look for a restriction in the oil passages of the oil
leakage in the supply side of the oil pump will also cause
cooler.  If the oil cooler has a restriction, the oil
cavitation and loss of oil pressure. If the bypass valve for
temperature will be higher than normal when the engine
the oil pump is held in the open (unseated) position, the
is operated. The oil pressure of the engine will not get
lubrication system can not get to maximum pressure. Oil
low just because the oil cooler has a restriction.
pump gears that have too much wear will cause a
reduction in oil pressure.
Also check the oil cooler bypass valve to see if it
is held in the open position (unseated). This condition
will let the oil through the valve instead of the oil cooler,
and oil temperature will increase.


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