TM 5-3805-290-23-1
THEORY OF OPERATION - CONTINUED
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ENGINE - CONTINUED
11.
Lubrication System.
a.
Lubrication system pressure is supplied by engine oil pump which uses rotors. Engine oil pump is driven by an
idler gear. Crankshaft gear drives idler gear. Engine oil pump has an inner rotor and an outer rotor. The rotors' axes
of rotation are off-center relative to each other. There is a key between inner rotor and drive shaft.
b.
Inner rotor has four lobes which mesh with five lobes of outer rotor. When inner lobe rotates, distance between
lobes of outer rotor and inner rotor increases in order to create suction. When distance between lobes decreases,
pressure is created.
c.
Lubricating oil from oil pan flows through a strainer and pipe to suction side of engine oil pump. Lubricating oil
flows from outlet side of pump through pipe and passage to filter head. Oil then flows from filter head through pipe
to plate type oil cooler. Oil cooler is located on left side of engine.
d.
From oil cooler, oil returns through pipe to filter head. Oil then flows from filter head to bypass valve and from
bypass valve to oil filter.
e.
Oil flows from oil filter through passage drilled across cylinder block to oil gallery. Oil gallery is drilled through
total length of left side of cylinder block. If oil filter is on right side of engine, oil flows through passage drilled
across cylinder block to pressure gallery.
f.
Lubricating oil from oil gallery flows through high pressure passages to crankshaft main bearings. Then, oil flows
through passages in crankshaft to connecting rod bearing journals. Pistons and cylinder bores are lubricated by
splashing of oil and oil mist.
g.
Lubricating oil from main bearings flows through passages in cylinder block to camshaft journals. Oil then flows
from second camshaft journal at reduced pressure to cylinder head. Oil then flows into rocker arm bushing of
rocker arm levers. Valve stems, valve springs, and valve lifters are lubricated by splashing and misting of oil.
h.
Idler gear hub is lubricated by oil from oil gallery. Timing gears are lubricated by splashing of oil.
i.
Turbocharger is lubricated by oil from oil filter passing through engine block. An external line from engine block
supplies oil to turbocharger. Oil then flows through a line to oil pan.
j.
Piston cooling jets are installed in turbocharged engines. Piston cooling jets are supplied with oil from oil gallery.
Piston cooling jets spray lubricating oil on underside of pistons in order to cool them.
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