What kind of gas are you using, if your thermo is mis-set or not working properly, you will get the knocking sound due to the fuel vapor igniting early. If the octane is too low that might be a contributing factor. I would have them check your thermostatic valve, i ride in 100 degree heat all the time and I never see my temp indicator bars increase, and my fan comes on too, occasionally at slow speeks.
Just some ideas!
"We do not quit playing because we grow old, we grow old because we quit playing."
Oliver Wendell Holmes