We have a Hayward Motor A.O Smith Model C48J2N131 3/4 HP on our pool and it has started making a noise but it runs what do we need to do?

sounds like you need a new motor or the capacitors are making noise if not new replace motor dont forget to replace seals also

Impeller could be plugged?
Diffuser may have become misaligned and hitting the impeller?
May have sucked up some foreign debris?
Knocking could be a bad bearing.

sounds like a seized bearing. they can be replaced at your local motor shop or pool store. now that its buzzing, i would also suggest getting the start capacitor replaced at the same time.

YOU WILL NEED TO REPLACE THE MOTOR.

DIRTY START switch or the motor is locked up, breaker off ! remove motor from tank body and see if the motor will turn over if it does could be the switch or the motor is shorted witch there is no fix but a new or rebuilt motor. search your area for your local pool pump motor repair guy with free testing..
Jay the pool pump motor repair guy longwood Fl

if its whining but still spinning, the bearings are done. If it just makes a loud noise, the capacitor could be bad or the bearings have seized.

Are you sure it was pumping water when you started it? and did you prime the pump before starting it up? if not prime the pump first.

A.O. Smith is just the motor. If your pump is a Hayward any pool store can help. Take your old one in and they can match it. Be sure to get a new seal while your at it, It should be a #201 seal. If you pull the whole motor and pump face the pool shop can probally do the work for you and gennerally don't charge except for the parts. Good luck

THIS IS LIKELY CAUSED BY SOMETHING IN IMPELLER TURN OFF POWER SEE IF YOU CAN SEE ANTHING IN IT YOU HAVE TO TURN HANDEL VALVES OFF PUSH DOWN IF YOU HAVE TO OPEN PIPE IN FRONT OF PUMP I