TM 5-3895-346-14
ENGINE OVERHAUL
LUBRICATION SYSTEM
LUBRICATION SYSTEM
The engine lubrication system, illustrated in Fig. 1, includes an oil in- take screen and tube assembly, an oil
pump, an oil pressure regulator valve, a full-flow oil filter with a bypass valve, an oil cooler, and oil cooler
bypass valve.
The rotor-type oil pump is bolted to the back of the engine lower front cover and is driven directly by the
crankshaft.
Lubricating oil from the pump passes from the lower front engine cover through short gallery passages in the
cylinder block. From the block, the oil flows to the full-flow filter, then through the oil cooler and back into the
front engine cover and cylinder block oil galleries for distribution to the various engine bearings. The drain from
the cylinder head and other engine parts leads back to the oil pan.
Clean engine oil is assured at all times by the use of a replaceable element-type full-flow filter. With this type
filter, which is installed between the oil pump and the oil cooler, all of the oil is filtered before entering the
engine. Should the filter become plugged, the oil will flow through a bypass valve, which opens at
approximately 18-21 psi (124-145 kPa) directly to the oil cooler.
On current engines, the oil cooler by-pass valve is located on the right-hand side of the engine front cover and
the oil pressure regulator valve is located on the left-hand side as viewed from the rear of the engine (Fig. 1).
On former engines, both valves were located on the right-hand side of the cover (Fig. 1).
If the cooler becomes plugged, the oil flow will be to a bypass valve in the lower engine front cover and then to
the cylinder block oil galleries. The bypass valve opens at approximately 52 psi (359 kPa) in the current in-line
engines. In the former in-line engines, the bypass valve opens at approximately 30 psi (207 kPa).
Stabilized lubricating oil pressure is maintained within the engine at all speeds, regardless of the oil
temperature, by means of a regulator valve located in the lower front engine cover. The regulator valve,
located in the pump outlet passage, opens at 51 psi (352 kPa) on in-line engines or 52 psi (359 kPa) on 6V
engines and returns excess oil directly to the crankcase.
Lubricating Oil Distribution
Oil from the oil cooler on the in-line engine is directed to the lower engine front cover and then to a longitudinal
main oil gallery in the cylinder block. As shown in Fig. 1, this gallery distributes the oil, under pressure, to the
main bearings and to a horizontal transverse passage at one end of the block and to vertical passages at each
corner of the block which provide lubrication for the balance shaft and camshaft bearings. The camshaft
bearings incorporate small slots through which lubricating oil is directed to the cam follower rollers.
Oil for lubricating the connecting-rod bearings, piston pins, and for cooling the piston head is provided through
the drilled crankshaft from the adjacent forward main bearings. The gear train is lubricated by the overflow of
oil from the camshaft pocket through a communicating passage into the flywheel housing. Some oil spills into
the flywheel housing from the bearings of the camshafts and balance shaft.
Drilled oil passages on the camshaft side of the cylinder head (Fig. 1) are supplied with oil from the bores
located at each end of the cylinder
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