I ride my 2013 XCT in stop and go traffic in NYC almost daily. Every time the engine temperature reaches 88 to 93 degrees, I hear a strange light knocking noise when I rev the engine. Like I said, this only happens when the engines gets really hot. On cooler days, or if there're no traffic, or if I'm riding on the highway, she sounds normal. Can anyone tell me why she makes this sound. You don't hear the light knocks when she idle, only when you hit throttle.