run the fan removed from the motor, you should feel the air blowing down from the fan.. it's not a wind machine, but provides more airflow over the motor can's built-in cooling fins than if you were rolling with no body on... certainly won't fix a hot motor that is over-geared/loaded, but I notice by the time I pull body clips after a run motor is cooler than it was without any fan...
If your motor can doesn't have the built-in cooling fins (like the older style brushless motors) it is less effective...