If the surface is corroded or if the blades are damaged, replace the impeller

Water Pump Impeller Disassembly/Assembly
Water Pump Housing DisassemblyTransmission Shaft Disassembly
Remove the transmission shafts (see Transmission Shaft
Removal).
Remove the circlips, and then disassemble the transmission
shafts.
Special Tool - Outside Circlip Pliers: 57001-144
The 5th gear [A] on the output shaft has three steel balls
assembled into it for the positive neutral fin ...
Piston Ring, Piston Ring Groove Wear Inspection
Check for uneven groove wear by inspecting the ring seating.
The rings should fit perfectly parallel to groove surfaces.
If not, replace the piston and all the piston rings.
With the piston rings in their grooves, make several measurements
with a thickness gauge [A] to determine pisto ...
Oil Pan Installation
If the oil filter holder bolt [A] was removed, tighten it.
Apply a non-permanent locking agent to the threads of
the oil filter holder bolt.
Torque - Oil Filter Holder Bolt: 35 N·m (3.6 kgf·m, 26 ft·lb)
Replace the O-rings [B] with new ones, and apply grease
to them.
Install the O-ri ...