3-168. LUBE OIL PRESSURE REGULATOR AND OIL BY-PASS VALVE.
The maintenance instructions for the lube oil pressure regulator and the oil by-pass valve are contained in
the following paragraphs:
Lube Oil Pressure Regulator
Oil By-pass Valve
3-168.1. LUBE OIL PRESSURE REGULATOR - MAINTENANCE INSTRUCTIONS.
a. Stabilized lubricating oil pressure is maintained within the engine at all speeds, regardless of oil
temperature, by means of a regulator installed between the oil pump outlet pipe and the cylinder block.
b. The regulator assembly consists of a body, a hollow piston-type valve, a compression spring, and a plug
to retain the spring in the body.
c. The valve is held on its seat by the spring, which is compressed by the plug screwed into the valve opening
in the regulator body. The entire assembly is bolted to the lower flange of the cylinder block and sealed against
oil leaks by a gasket between the two members. When conditions are such that the oil pressure at the valve
exceeds 50 pounds per square inch (35.2 kg/cm sq) the valve is forced from its seat and oil from the engine
gallery is by-passed to the engine oil pan. Thus, stabilized lubricating oil pressure is maintained at all times
regardless of oil temperature.
d. Under normal conditions, the pressure regulator should require very little attention. If sludge has been
allowed to accumulate in the lubricating system, the valve may not work freely, thereby remaining open or
failing to open at the normal operating pressure.
e. Whenever the lubricating oil pump is removed for inspection, the regulator valve and spring should also be
removed, thoroughly cleaned in fuel oil and inspected.