TM 5-3805-291-23-1
THEORY OF OPERATION - CONTINUED
0003 00
ENGINE - CONTINUED
(2)
High pressure relief valve regulates high pressure in system. Valve allows oil to return to sump when oil
pump discharge pressure reaches 100 psi (690 kPa). Oil then flows through engine oil cooler, which uses
engine coolant to cool oil. Oil cooler bypass valve directs oil flow through engine oil cooler by two differ-
ent methods:
(a) Oil cooler bypass valve will open when oil pressure exceeds 29 psi (200 kPa). Opening bypass valve
will bypass oil through engine oil cooler.
(b) Oil flows toward primary engine oil filter. When oil pressure differential across oil filter bypass valve
reaches 29 psi (200 kPa), valve allows oil flow to bypass primary engine oil filter to lubricate engine
parts. Bypass valve provides immediate lubrication to engine components when there is a restriction
in primary engine oil filter due to cold oil with high viscosity or a plugged primary engine oil filter.
427-C1713
(3)
Filtered oil flows through main oil gallery in cylinder block to these components:
Piston cooling jets
Valve mechanisms
Camshaft bearings
Crankshaft main bearings
Turbocharger
(4)
Piston cooling jets provide piston undersides with liberal amounts of oil to remove heat from pistons. Oil
is also used as a lubricant.
(5)
Breather allows engine blowby to escape from crankcase. Engine blowby is discharged into atmosphere
through a hose. This prevents pressure from building up inside crankcase that could cause seals or gaskets
to leak.
0003 00-6
