10-13. VACUUM PUMP.
10-14. GENERAL. The vacuum pump is of the rotary vane, positive displacement type. This unit consists
essentially of an aluminum housing containing a tempered sleeve in which an offset rotor is incorporated. This
assembly is driven by means of a coupling mated to the engine driven gear assembly. The pump is mounted on
the accessory section of the engine.
10-15. TROUBLESHOOTING. For troubleshooting of the pumps, refer to Table X-l of this section.
10-16. REMOVAL OF VACUUM PUMP. The vacuum pump can be removed by the following procedure:
a. Remove the top portion of the engine cowling.
b. Loosen the hose clamp and remove the hose from the vacuum pump fitting.
c. Remove the vacuum pump by removing the four retaining nuts, lock washer and plain washers.
10-17. REPLACING PUMP FITTINGS.
a. Before installing any fittings on the pump, check for any external damage. A pump that has been
damaged or dropped should not be installed.
b. When a vise is used to hold the pump while installing fittings, suitable caution must be exercised to avoid
pump damage. The square mounting flange must be held between soft wood blocks and only at right angles to
the vise jaws. Use only enough vise pressure to hold the pump firmly.
—CAUTION —
DO NOT apply vise pressure to the outside diameter or overall length of
the pump.
c. The ports of the AIRBORNE pump have been treated with a dry film lubricant and the AIRBORNE
fittings are cadmium plated thus eliminating any need for thread lubricants. If thread lubricant is required, use a
powdered moly-sulfide or graphite in dry form or in an evaporating vehicle; or employ a silicone spray. Apply
sparingly to external threads of fittings only.
Trouble
Cause
Remedy
Vacuum correct but
Regulator sticky.
Clean regulator.
pilot reports pressure
erratic or shows complete
Oil in pump due to
Replace pump.
loss in flight.
leaky engine seal or
cleaning fluid blown
into pump while cleaning
engine.
Pressure can only be
Leak in system.
Repair or replace lines.
maintained at full
throttle on ground.
Worn pump.
Replace pump.
Stuck regulator.
Clean or replace
regulator.
PIPER AIRCRAFT
PA-28-161 CADET
AIRPLANE MAINTENANCE MANUAL
Issued: FEBRUARY. 28, 1989
I N S T R U M E N T
2B14
TABLE X-I. VACUUM SYSTEM (cont.)