Adjusted valves on 1990 Camaro 305 and what I think is knock sensor got broken. It's located in right head between plugs #6 & 8. The fan didn't come on when temp got high and I took it to a friend that does some work on it. He said it's the temp sensor but I don't know. If a/c is switched on the fan comes on, so it worlks. Wondering if the sensor broken is part of problem w/fan not turning on with high temp. Please help diagnose....