Dirt and other contaminants are agents that create a low pH in
Oil with a viscosity which is too low or contamination of the oil
by particulate materials increases the wear on all engine parts.
Low Oil Pressure
The following conditions will cause low oil pressure:
The oil level is low in the crankcase.
A restriction exists on the oil pump screen.
Connections in the oil lines are leaking.
The connecting rod or the main bearings are worn.
The rotors in the oil pump are worn.
The oil pressure relief valve is operating incorrectly.
A worn oil pressure relief valve can allow oil to leak through the
valve which lowers the oil pressure. Refer to Specifications,
"Engine Oil Bypass Valve" for the correct operating pressure
and other information.
When an engine that is turbocharged runs at the normal
temperature for operation and at high idle, the oil pressure
must be a minimum of 280 kPa (41 psi). A lower pressure is
normal at low idle.
4C-4890 Hydraulic Test Group can be used in order to test the
pressure of the lubrication system.
High Oil Pressure
High oil pressure can be caused by the following conditions:
The spring for the oil pressure relief valve is installed
The plunger for the oil pressure relief valve becomes
jammed in the closed position.
Excessive sludge exists in the oil which makes the
viscosity of the oil too high.
Excessive Component Wear
Premature component wear can be caused by the following
Particulate materials are in the engine oil which causes
abrasion of moving parts.
A restricted passage in the engine for the lubricating oil
prevents the oil from lubricating a moving part or cooling
Low oil pressure prevents an adequate flow of oil to the
Lubricating oil should be changed at the times which are
specified in Operation And Maintenance, "Maintenance Interval
Schedule". The type of lubricating oil is specified in Operation
And Maintenance, "Lubricant Specifications".
SMCS Code: 1350
This engine has a pressure type cooling system. A pressure
type cooling system gives two advantages:
The pressure type cooling system can operate safely at
a higher temperature than the boiling point of water at a
range of atmospheric pressures.
The pressure type cooling system prevents cavitation in
the water pump.
Cavitation is the sudden generation of low pressure bubbles in
liquids by mechanical forces. The generation of an air or
steam pocket is much more difficult in a pressure type cooling
Regular inspections of the cooling system should be made in
order to identify problems before damage can occur. Visually
inspect the cooling system before tests are made with the test
Visual Inspection Of The Cooling System
Check the coolant level in the cooling system.
Look for leaks in the system.
Inspect the radiator for bent fins and other restriction to
the flow of air through the radiator.
Inspect the drive belt for the fan.
Inspect the blades of the fan for damage.
Look for air or combustion gas in the cooling system.