Hello....I've the noise described on these forums typically while idling. The only difference is that it comes and goes while driving down the street?? It's a humming-type noise that I thought maybe the air conditioning system but when turned off, it will still make the noise. It isn't constant but comes and goes. This is my daughters car - 99 2.5 6 with 125,000 miles. It's driving her nuts!! Any suggestions or ideas would be appreciated!


Thanks!

I have noticed the same issue with my 01 and found it to be the water pump tensioner pulley. Both tensioners were making noise at idle but that humming during driving was the water pump tensioner bearings. Doesn't look like I can change the bearings or get it aftermarketso I will be checking with the dealer tomorrow. Anyone have any insight to this as far as aftermarket?

FYI...water pump belt tensioner was $45 from the dealer. This took about 10 min to get off and another ten to put it back on. Once the old one was off I could hear the bearings rumbling very distinctly when I spun the pulley. Woohoo! No more moose on my Merc!