Help please!

[FunFun47]

Hi everyone. I am having trouble with my brushles sensorlesss esc, for some reason it will not run for 5 mins it will do 4.50 Max before the esc cuts out. I originally thought it was just getting too hot and the gearing was wrong, but its not at all hot nor is the motor. I an running 80-18 gearing and the car is an Ansmann mad rat. I am a nitro driver and am new to the electric and wondered if anyone had any ideas on what's happen i ng. think there motor might be on the way out