7-1.4.4 Thrust Plates (5 and 11).
a. The thrust plates seal the gear section at the sides of the gears. Wear here will allow internal slippage, that is,
oil will bypass within the pump. .002" maximum wear is allowable. Replace thrust plates if they are scored,
eroded, or pitted.
b. Check center of thrust plates where the gears mesh. Erosion here indicates oil contamination.
c. Pitted thrust plates indicate cavitation or oil aeration.
d. Discolored thrust plates indicate overheating, probably insufficient oi.
7-1.4.5 Bearings (16). If gears are replaced, bearings must be replaced. Bearings should fit into bore with a light press
fit. A neat hand fit is allowable. If bearings can fall out, bore may be oversize.
7-1.4.6 Seals and Gaskets. Replace all rubber and polymer seals whenever disassembling pump. Include all "O" rings
(17), pocket seals (14) behind thrust plates, shaft seal (20), and gasket seals (15).
7-1.5 Assembly.
a. Stone off all machined surfaces with a medium grit carborundum stone.
b. If bearings (16) have been removed, deburr bearing bores. Rinse parts in a solvent. Air blast all parts and wipe
with a clean lintless cloth before starting assembly.
c. Grip shaft end cover (13) in vise with mounting face down. Examine plug or 2 check valves (21) to be sure
they're tightly in place. Replacement is necessary only if parts are damaged. Remove with screwdriver or
special check valve tool (see figure 7-1).
d. If plug or check valves (21) are being replaced, screw in new parts tightly. Stake plug with prick punch at both
ends of screwdriver slot and around edges. Screw check valves in tightly with tool. Peen edge of hole 1/32" to
1/16" with 14" diameter steel ball.
e. If ring seals (17) are being replaced insert into bottom of drive gear bearing bore. The notch in the ring seal
MUST BE VISIBLE. This is a check to be certain the notched side is next to the bearing.
f. If any bearings (16) have been removed from the shaft end cover (13), port end cover (4), or bearing carrier (9),
replace the bearings by pressing them into the bearing bore with an arbor press.
g. Before inserting a new lip seal (20) in the shaft end cover (13), coat the outer edge of the lip seal and its recess
with Permatex Aviation Form-A-Gasket No. 3 Non-hardening Sealant or equivalent. With the metal side of the
lip seal up, press it into the mounting flange side of the shaft end cover with an arbor press
7-7
