TM 5-3895-383-24
Too Much Bearing Wear
When some components of the engine show bearing wear in a
short time, the cause can be a restriction in an oil passage.
If the gauge for oil pressure shows enough oil pressure, but a
component is worn because it cannot get enough lubrication,
look at the passage for oil supply to the component. A
restriction in a supply passage will not let enough lubrication
get to a component, and this will cause early wear.
Increased Oil Temperature
With the engine at operating temperature (using SAE 10W30
oil), the maximum oil temperature is 115°C (239°F).
Look for a restriction in the oil passages of the oil cooler. If the
oil cooler has a restriction, the oil temperature will be higher
than normal when the engine is operated. The oil pressure of
the engine will not get low just because the oil cooler has a
restriction.
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.
Gauges For Oil Pressure
Tools Needed
1U5470
Engine Pressure Group
1
An oil pressure gauge or a sender that has a defect can give
an indication of low or high oil pressure.
The 1U5470 Engine Pressure Group can be used to make a
comparison with instrument panel gauges.
The 1U5470 Engine Pressure Group can be used to measure
the pressure in the system. This tool group has a gauge to
read pressure in the oil manifold. Special Instruction,
SEHS8907 is with the tool group and gives instructions for its
use.
Cooling System
These engines have a pressure type cooling system. A
pressure type cooling system gives two advantages. The first
advantage is that the cooling system can have safe operation
at a temperature that is higher than the normal boiling (steam)
point of water. The second advantage is that this type system
prevents cavitation (low pressure bubbles suddenly made in
liquids by mechanical forces) in the water pump. With this type
system, it is more difficult for an air or steam pocket to be
made in the cooling system.
The cause for increased engine temperature is generally
because regular inspections of the cooling system were not
made. Make a visual inspection of the cooling system before a
test is made with test equipment.
Visual Inspection Of The Cooling System
1.
Check coolant level in the cooling system.
2.
Look for leaks in the system.
3.
Look for bent radiator fins. Be sure that air flow through
the radiator does not have a restriction.
4.
Inspect the drive belts for the fan.
5.
Check for damage to the fan blades.
6.
Look for air or combustion gas in the cooling system.
7.
Inspect the filler cap and the surface that seals the cap.
This surface must be clean.
Testing The Cooling System
Remember that temperature and pressure work together.
When a diagnosis is made of a cooling system problem,
temperature and pressure must both be checked. Cooling
system pressure will have an effect on coolant boiling
temperatures. For an example, look at the chart to see the
effect of pressure and height above sea level on the boiling
(steam) point of water.
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