Was in a rush earlier, (wow, way earlier) and after reading your reply I realized i forgot to provide probably some pretty useful info... The tensioner and idler have been changed within past 10 days. At that time I decoupled the power steering pump and the water pump so that I could spin each indep...

2008 XC90 3.2 FWD 280,000 miles. Sounds like marbles in a can or shaking a can of spray paint right when started until it is shut off. Using my mechanic scope it seems like it is coming from the AC Compressor, it blows cold air all day long.. If I release the belt tension and pin the tensioner then ...