(Disclaimer: Read and follow your equipment manufacturer's recommendations! Every piece of equipment and every installation is unique. Do not attempt to complete work that you are not qualified to complete. These are general ideas and this information does not constitute specific advice to be acted on prior to consulting a professional.)
We got lucky on this one: We walked into a pump room recently and immediately noticed extreme heat radiating off of one of the 30 HP pumps. The heat was so intense that it stopped us in our tracks. We speak often about how important it is that pool operators use all 5 of their senses (well....maybe not taste) ... to take in information. Well, we smelled an electrical burn smell and immediately felt the heat coming off of this motor from about 10 feet away. We investigated to find the fan blade on the back of the motor had broken into about 15 pieces so this motor had no mechanical cooling on it.
The placard on the motor listed a max ambient operating temperature of 104 degrees fahrenheit. Contrary to one's instinct, we didn't turn the motor right off. We were at risk of melting internal parts (coatings, rings, seals, etc), but we opted to run (fast) and fetch a carpet blower fan and placed it right behind the pump blowing directly on the motor to try and cool it down before killing power.
We also used a garden hose to spray the housing to assist in the cooling.
We monitored the motor temperature with a thermocouple (Fluke meter). Hard to believe, but the temp we measured initially was 204 degrees.
After 20 minutes of fan/spray...the temp got back to 80 degrees.
At this point, we felt it was safe to turn the motor off and to make the repair. We locked/tagged out, removed the broken fan blade parts, and carefully installed the spare fan blade.
When installing these, be sure the keyway notch is correctly lined up, and never use the actual blades as a handle. The blades are very fragile - use the center of mass to push and pry when installing this part.
We reinstalled the housing (cover) and ensured the blade rotated freely without rubbing anything. We then fired it back up and monitored the heat dissipation to ensure all was working.