HI, I am new to posting to the Buick Forums here, though I have read many over the years and am grateful for much good advice. I have an 87 GN that I have had for almost 30 years, with high miles. Recently, I have had trouble with the serpentine belts crapping out. I have put three new ones on in the last month (not cheap ones either) and within about 5 minutes of idling, they somehow start coming apart on the engine side of the belt. I have checked all the pulleys etc. and don't see any way they should be getting cut. The only thing out of the ordinary I noticed was the tensioner sort of 'pulsating' when the engine idles low. Has anyone else had this type of problem? This is the first time I've encountered it.