Look, Listen and Feel
What am I hearing?
Any noise that is coming out of the pool pump should be marked in your mind. Regardless of the age of your pump get to know it well and listen to it often, at least daily. Make no mistake, just cleaning the lint strainer isn't inspecting your pump. If the sound from your pump changes dramatically start looking for a reason.
What am I looking for?
Grab a light and look the entire pump and electric motor over carefully.
Is the paint on the pump or motor peeling, is there visible pitting if so the bonding may have failed. Is there water leaking from the pump(check the fasteners)if you have a mechanical seal in the pump it shouldn't be leaking. If you have an older pump with braided packing you'll want some leakage about 1-2 drops per minute.
What am I feeling?
The first place you want to check is the bearing areas of the electric motor.
Caution*: Use the back of your hand to check these areas, back of your hand only!
If the motor has an electrical short the current if it reaches the backside of your hand will cause the muscles in your arm to retract your hand from the motor. The back of your hand is also more sensitive to heat and that is what you are looking for, in the motor and the pump. Using your hands will allow you to feel for any abnormal vibrations that may indicate serious problems.
Most of the major manufacturers of commercial pool pumps have their electric motors fitted with grease zerks for lubricating the electric motor bearings,(usually Chevron SRI) no more than 1-2 shots each zerk annually.
The pump volute case needs to be opened annually. Most modern pool pumps have the interior of the pump volute case coated with a corrosion resistant epoxy coating.
The impeller, volute case, backing plate and the impeller wear ring should be inspected for cavitation pitting, corrosion or any other obvious wear, replace parts as needed. Reassemble the pump with new gaskets and a new mechanical seal. Depending on the amount of wear noted, these inspections can be extended out to eighteen months or two years.
"Happy Pump, Happy Pool" Bob Walker