PIPER SENECA II SERVICE MANUAL
6-4. HYDRAULIC PUMP (ORIGINAL EQUIPMENT - PRESTOLITE).
6-5. REMOVAL.
The hydraulic pump with reservoir incorporated is located in the nose section of the fuselage. Access to
the pump is through the access panel in the nose baggage compartment.
a. Disconnect the pump electrical leads from the pump solenoid relays and the ground wire from the
battery shelf.
b. Disconnect the hydraulic lines from the pump. Cap the line ends to prevent contamination.
c. Remove pump by removing pump attaching bolts.
6-6. DISASSEMBLY. (Refer to Figure 6-3.)
After the hydraulic pump has been removed from the airplane, cap or plug all ports, and clean exterior of
pump using a dry cleaning solvent to remove accumulated dirt and dust. The three major components of
the pump assembly are the pump base, pump motor, and valve and gear case. These three major
components should be disassembled as follows:
a. Pump Base: Remove pump base (16) from valve and gear case by:
1. Cutting safety wire and removing bolts (17) with washers securing pump base to pump and
gear case.
2. The check valve within the pump base should be removed for cleaning purposes only. To
remove valve, cut safety wire and remove bolt, spring and steel ball. Replace O-ring at
reassembly.
b. Pump Motor: The pump motor may be removed from the pump and disassembled as follows:
1. Remove thru bolts (4) from head (1) of motor. Using a knife cut the seal coating between the
motor head and case.
2. Lift the head up from the case approximately .50 of an inch, this will allow inspection of
brushes (3) without the brushes unseating from the commutator. (Refer to Paragraph 6-7 for
brush inspection.) The brush leads are secured to the head assembly.
3. Raise the head assembly (1) off the armature (8) and note the small thrust ball (7) located
between the end of the armature (8) and motor head. Do not misplace this bearing.
4. Draw the armature from the motor frame (9). Note the number of thrust washers ( 1 ) mounted
on the drive end of the armature shaft.
5. Remove the motor frame from the pump reservoir (13).
c. Valve and Gear Case: Remove valve and gear case (15) from reservoir (13) as follows:
1. Remove eight screws from flange of body and separate the two assemblies (18).
2. Pump gears and valves should be removed for cleaning purposes only. To remove cap securing
gears, remove attaching bolts. The two valve springs should be positively identified with their
cavities; otherwise, it will be necessary to readjust each valve for proper operating pressure.
01/01/09 VI - HYDRAULIC SYSTEM
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