Section XII. OIL PUMP AND OIL PAN ASSEMBLY
The gear-type oil pump is mounted on the
front of the cylinder block and the drive gear meshes
with the crankshaft gear.
b. A reIief valve, located in the oil pump out-
let, bypasses oil back to the oil pan when the press-
ure exceeds 82 to 98 psi. This relieves excessive
discharge pressure when starting a cold engine and
cuts down wear on the oil pump gears.
The oil pan serves as a bottom cover for
the crankshaft and a reservoir for the lubricating
oil. A finned steel tube is installed in the oil pan.
Heated coolant is circulated through the tube to pre-
heat the oil to aid in engine starting in sub-freezing
14-65. Removal and Disassembly.
Symptoms and Isolation of Malfunction. A
malfunction of the oil pump or a leak in the oil pump
is usually indicated by 10SS of oil pressure which re-
sults in engine shutdown.
To isolate the malfunction,
proceed as follows
(1) Examine the oil pan for evidence of
leakage. Leaking oil can be detected on top of the
fuel tank located directly below the oil pan.
(2) Check the oiI Ievel If the level iS suff-
cient for normal operation, and engine has shut-down
due to loss of oil pressure, the malfunction is prob-
ably the result of oil pump failure. Isolate oil pump
failure as follows:
(a) Remove valve cover. Refer to TM
5-6115-545-12 and start engine. Before releasing
start switch move the battle short switch to the ON
position to by-pass the low oil pressure cut-out switch.
(b) If there is sufficient pressure from
the oil pump, Gil should be forced out of the rocker
arm shaft above each cylinder. If there is no evi-
dence of oil flow at these points, the oil pump has
failed. Stop the engine and proceed with the removal
and repair procedures.
b. Removal and Disassembly.
(1) Drain fuel system and remove main fuel
(2) Remove electric starter, tool box and
fuel-burning heater if installed. Refer to Operator
and Organizational Maintenance Manual
(3) Open oil pan drain valve and allow oil
(4) Close valves for coolant inlet and outlet
to the engine block if a winterization kit is
(5) Disconnect coolant inlet and outlet lines
to oil pan heater element if winterization kit is installed.
Refer to TM 5-6115-545-12 for winterization kit.
(6) Disconnect oil drain hose.
(7) Refer to figure 14-30 and remove and
disassemble the oil pan and heater as follows
(a) Remove 32 capscrews and lock-
washers securing the oil pan to the flywheel housing,
timing gear cover, and the cylinder block
(b) Jar the oil pan loose, drop the rear
end, and remove pan.
(c) Remove the brass fittings from the
inside and Outside of the connections on the oil pan.
(d) Remove the nuts, lockwashers, and
capscrews securing the heater element clamps to
the inside of the oil pan.
Remove the heater element
(8) See figures 14-31 and 14-32 and re-
move and disassemble the oil pump as follows:
(a) Remove the clamp supporting the
oil suction tube.
(b) Uncouple the brass compression
fitting securing the oil pump discharge tube.
(c) Remove the bolts securing the oil
pump to the cylinder block and remove the oil pump
assembly. The pump may have to be pried off its
(d) Remove the oil pump suction tube
support bracket from the main bearing cap.
(e) Wash the oil pump assembly in
cleaning solvent, Federal Specification P-D-680.
(f) Remove the suction tube assembly.
(g) Remove the pressure relief valve
assembly from the pump body.
(h) Depress the relief valve spring and
retainer with two screwdrivers or on improvised
Drive out the roll pin and remove
retainer, spring and relief valve piston.
(i) Remove the oil pump drive gear
from the driveshaft. Use a three-leg puller to
avoid damage to the gear.
(j) Remove the screws and washers
securing the pump cover to the body assembly and
remove the pump cover.
(k) Remove the pump driver gear and