Thermo King 914970, Manual

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93
Engine Maintenance
Engine Lubrication System
The TK 3.95 engine has a pressure lubrication
system. A trochoid type oil pump circulates the oil
through the system to lubricate the engine
compartments. The oil pump is driven by the
crankshaft gear, and is attached to the lower part
of the timing gear housing.
The oil is picked up by a screened inlet near the
bottom of the oil pan. The inlet is positioned far
enough from the bottom of the pan to avoid
picking up any of the residue that tends to settle
on the bottom of the pan. The oil then passes
through the intake pipe to the oil pump.
The oil pump forces a large volume of high
pressure oil through an oil gallery to the oil filter.
Dirt and other particles are trapped in the filter
element as the oil passes through the oil filter. If
the filter element becomes clogged, a bypass
valve built into the oil filter allows the oil to
bypass the filter element. This keeps the engine
components from being starved for oil if the filter
element is clogged.
After passing through the oil filter, the oil is still at
high pressure when it reaches the oil pressure
control valve and the main oil gallery. The oil
pressure control valve limits the oil pressure in the
main oil gallery to approximately 43 to 57 psi
(294 to 392 kPa) by diverting the excess oil back
into the oil pan. Oil passages connected to the
main oil gallery supply oil to the idler gear shaft,
the fuel injection pump, and to each main bearing.
Oil from the idler gear shaft lubricates the idler
gear bushing, the idler gear, and the other timing
gears before returning to the oil pan.
The oil that flows to the fuel injection pump
returns to the oil pan after lubricating the injection
pump components.
Some of the oil supplied to the main bearings
flows through passages in the crankshaft to the
connecting rod bearings. This oil is thrown around
the bottom end of the engine as it flows out of the
bearings while the crankshaft rotates. Some of this
oil lubricates the cylinder walls. Some of this oil
lands in the holes on the top of the connecting
rods and lubricates the wrist pins and the
connecting rod bushings. The oil eventually
returns to the oil pan.
Some of the oil supplied to the main bearings
flows through passages in the cylinder block to
the camshaft bearings. From there some of the oil
flows through passages in the cylinder block, the
cylinder head, and the rocker arm supports to the
rocker arm shaft. The rocker arm shaft supplies oil
to the rocker arm bushings and the rocker arms.
Some oil squirts out of holes in the rocker arms to
lubricate the valve stem caps and the valve stems.
The oil that is pumped up to the rocker arm
assembly flows back down through the push rod
openings and lubricates the tappets and the cam
lobes as it returns to the oil pan.
Oil pressure is affected by oil temperature, oil
viscosity, and engine speed. Low oil pressure can
usually be traced to the lack of oil, a faulty oil
pressure control valve, loose connections in the
lubrication system, or worn bearings. Low oil
pressure is not normally caused by a faulty oil
pump.
Engine Oil Change
The engine oil should be changed according to the
“Maintenance Inspection Schedule”. Drain the oil
only when the engine is hot to ensure that all the
oil drains out. When changing oil, try to make
sure that the unit is not tipped away from the
direction that the oil is supposed to flow out of the
oil pan. It is important to drain as much of the
residual oil as possible because most of the dirt
particles are in the last few quarts of oil that are
drained from the oil pan. Refill the oil pan (refer
to the “Specifications” chapter) and check the oil
level. Run the unit, and then recheck the oil level.
Add oil as necessary to reach the full mark on the
dipstick. See the Specifications page for the
correct type of oil.