I have a 1999 ML 320. The power steering started to make a winding noise, it progessively got loader and loader. No leaks in the pump were noticable, no loss of fluid. It would wind excessively when turning the wheel so I concluded it had to be the pump. I replaced the pump and the noise seemed to have gone away but within few days of driving it has returned, although not quite as load. Any ideas what else this could be, I checked the serpintine belt and it shows no signs of where.
JP