My van started with a chirp and then got a whining noise too ,that started within days of each other. Took van to mechanic. He replaced the idler pulley and put a new serpentine belt on. worked for a day great no chirp no whine.The next day the whine was back no chirp. only as I was sitting in idle the whining stopped but when I pulled out the whinning was back and I had no power but then it surged. Did this as I was driving home. Deccided it was safer to drop off at my mechanic's garage. Got an educated idea of what might be causing this?