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

Water Pump Impeller Disassembly/Assembly
Water Pump Housing DisassemblyTransmission Shaft Assembly
Apply molybdenum disulfide oil solution to the sliding surfaces
of the gears and shafts.
Install the gears and the gear bushings [A] with their holes
[B] aligned.
Replace any circlips removed with new ones.
Install the circlips [A] so that the opening [B] of it is aligned
with ...
Thermostat Inspection
Remove the thermostat (see Thermostat Removal).
Inspect the thermostat valve [A] at room temperature.
If the valve is open, replace the thermostat with a new
one.
To check valve opening temperature, suspend the thermostat
[A] in a container of water and raise the temperature
of ...
Tire Tread Wear Inspection
As the tire tread wears down, the tire becomes more susceptible
to puncture and failure. An accepted estimate is
that 90% of all tire failures occur during the last 10% of tread
life (90% worn). So it is false economy and unsafe to use
the tires until they are bald.
Measure the tread depth a ...