- Hello, I have a 02 gmc envoy with the 4.2 i6 and 187,000 miles on it. Ok here is my issue, when I start the engine the fan belt slides to the rear of the water pump pulley and in turn slides to the rear of the A/C pulley. I have replaced belt tensioner, idler pulley, belt, water pump, water pump pulley and still the same problems persist. I finally just put on a shorter belt to bypass the A/C for now. Even with the shorter belt you can still see the, belt move back on the water pump pulley when engine is started but it works for now. I don't know what to do or where to go from here. Is it the a/c clutch or am I missing something. Any help is greatly appreciated. Thanks