Standard Practices - Engine - Piper Navajo Chieftain PA-31-350 Service Manual

Pressure oil from the cooler returns to a second threaded connection on the accessory housing from which
point a drilled passage conducts the oil to the oil pressure filter. In the event that cold oil or an obstruction
should restrict the oil flow to the cooler, an oil cooler bypass valve is provided to pass the oil directly from the
oil pump to the oil pressure filter.
The oil filter element, located on the accessory housing, provides a means of filtering from the oil any
solid particles that may have passed through the suction screen in the sump. After being filtered, the oil is fed
through a drilled passage to the oil pressure relief valve, located in the upper right side of the crankcase in
front of the accessory housing. This relief valve regulates the engine oil pressure by allowing excessive oil to
return to the sump, while the balance of the pressure oil is fed to the main oil gallery in the right half of the
crankcase. Residual oil is returned by gravity to the sump, where after passing through a screen it is again
circulated through the engine.
8-3.
STANDARD PRACTICES - ENGINE. The following suggestions should be applied wherever they
are needed, when working on the power plant.
a. To insure proper installation and/or assembly, tag and mark all parts, clips, and brackets as to their
location prior to their removal and / or disassembly.
b. During removal of various tubes or engine parts, inspect them for indications of scoring, burning
or other undesirable conditions. To facilitate reinstallation, observe the location of each part during removal.
Tag any unserviceable part and / or units for investigation and possible repair.
c. Extreme care must be taken to prevent foreign matter from entering the engine. such as lockwire
washers, nuts, dirt. dust, etc. This precaution applies whenever work is done on the engine, either on or off the
aircraft. Suitable protective caps, plugs and covers must be used to protect all openings as they are exposed.
NOTE
Dust caps used to protect open lines must always be installed
OVER the tube ends and NOT IN the tube ends. Flow through
the lines may be blocked off if lines are inadvertently installed
with a dust cap in the tube ends.
d. Should any items be dropped into the engine, the assembly process must stop and the item must be
removed, even though this may require considerable time and labor. Insure that all parts are thoroughly clean
before assembling.
e. Never reuse any lockwire, lock washers, tab locks, tab washers or cotter pins. All lockwire and
cotter pins must fit snugly in holes drilled in studs and bolts for locking purposes. Cotter pins should be
installed so the head fits into the castellation of the nut, and unless otherwise specified, bend one end of the
pin back over the stud or bolt and the other end down flat against the nut. Use only corrosion resistant steel
lockwire and / or cotter pins. Bushing plugs shall be lockwired to the assembly base or case. Do not lockwire
the plug to the bushing.
f. All gaskets, packings and rubber parts must be replaced with new items of the same type at
reassembly. Insure the new nonmetallic parts being installed show no sign of having deteriorated in storage.
g. When installing engine parts which require the use of a hammer to facilitate assembly or installation,
use only a plastic or rawhide hammer.
h. Whenever adhesive tape has been applied to any part, the tape and all residue must be removed
and thoroughly cleaned with petroleum solvents prior to being subjected to high temperature during engine
run. This would also apply to parts that have corrosion preventive compounds applied.
CAUTION
Ensure that anti-seize compounds are applied in thin even coats,
and that excess compound is completely removed to avoid
contamination of adjacent parts.
Revised: 3/31/94
POWER PLANT
2H6
NAVAJO CHIEFTAIN SERVICE MANUAL