Lubrication System; Adjustment Of Oil Pressure Relief Valve; Oil Screen; Oil Filter Element - Piper Navajo Chieftain PA-31-350 Service Manual

NAVAJO CHIEFTAIN SERVICE MANUAL
8-87. LUBRICATION SYSTEM.
8-88. ADJUSTMENT OF OIL PRESSURE RELIEF VALVE. Engines are furnished with an adjustable oil
pressure relief valve, which enables the operator to maintain engine oil pressure within the specified limits
(60 to 90 psi). The valve is located above and to the rear of No. 5 cylinder. If the pressure under normal
operating conditions should consistently exceed 90 psi or run less than 60 psi, adjust valve as follows:
a.
With the engine thoroughly warmed up and running at a maximum of 2200 RPM, observe the
reading on the oil pressure gauge. If the pressure is above 90 psi, stop engine, loosen the adjusting locknut,
and back off the adjusting screw one or two full turns. Tighten locknut and retest.
b.
If pressure is too low, turn adjusting screw further into the relief valve plug, thereby increasing
the tension on the relief valve spring. When the valve has been satisfactorily adjusted, tighten the locknut
and lockwire the crown nut to the drilled ear projecting from the valve mounting boss.
8-89. OIL SCREEN. The suction screen located in the left side of the engine sump should be cleaned at
each oil change to remove any accumulation of sludge and to examine for metal filings or chips. If metal
particles are found in the screen, the engine should be examined for internal damage. The suction screen is
removed from the sump by removing the hex head plug at the lower left side of the sump. Clean and
inspect the screen and gasket and replace the gasket if over compressed or damaged.
8-90. OIL FILTER ELEMENT.
a.
The oil filter element should be replaced after each fifty hours of engine operation: this is
accomplished by removing the lock wire from the bolt-head at the end of the filter housing, loosening the
bolt, and removing the filter assembly from the adapter.
b.
Before discarding the filter element, remove the outer perforated paper cover, and using a sharp
knife, cut through the folds of the element at both ends, close to the metal caps. Then, carefully unfold the
pleated element and examine the material trapped in the filter for evidence of internal engine damage such
as chips or particles from bearings. In new or newly overhauled engines, some small particle of metallic
shavings might be found; these are generally of no consequence and should not be confused with particles
produced by impacting, abrasion or pressure. Evidence of internal engine damage found in the oil filter
justifies further examination to determine the cause.
c.
After the element has been replaced, tighten the attaching bolt with 20 to 25 foot-pounds
torque. Lock wire the bolt through the loops on the side of the housing to the drilled head of the
thermostatic valve. Be sure the lock wire is replaced at both the attaching bolt head and the thermostatic oil
cooler bypass valve. Refer to latest revision of Lycoming Service Letter No. L157.
8-91. RECOMMENDATIONS FOR CHANGING OIL. (Refer to latest revision of Lycoming Service
Instruction No. 1014.)
a.
In engines that have been operating on straight mineral oil for several hundred hours, a change to
additive oil should be made with a degree of caution, since the cleaning action of some additive oils will
tend to loosen sludge deposits and cause plugged oil passages. When an engine has been operating on
straight mineral oil and is known to be in excessively dirty condition, the switch to additive or compounded
oil should be deferred until after the engine is overhauled.
b.
When changing from straight mineral oil to compounded oil, the following precautionary steps
should be taken:
1.
Do not add additive oil to straight mineral oil. Drain the straight mineral oil from the engine
and fill with additive oil.
2.
Do not operate the engine longer than five hours before the first oil change.
3.
Check all oil screens for evidence of sludge or plugging. Change oil every ten hours if sludge
conditions are evident. Resume normal oil drain periods after sludge conditions improve.
Revised: 3/11/81 POWER PLANT
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