Rattling noise that seems to come from the alternator,but is apparently not that...

[Razzorider]

I have a 2007 xc90 3.2L, I bought it 45 days ago. Since purchased, problems have arisen. I have replaced the fuel pump and sending unit, front brakes, 4 new tires, headlights, AC blower motor and resistor, and then It developed a rattling noise that seemed to come from the ac compressor area. The Volvo dealership told me it was the compressor clutch. I replaced the compressor and clutch with a new unit. Still have the noise. Then they told me it was the water pump, possibly but unlikely the tensioner pulley or idler pulley. I replaced all three and belt, also checking the power steering pump while I was in there. Which was fine. Wow, the water pump was fun.

So far over $1300 in parts and numerous hours of work, I still have the noise. Now the same Volvo dealership tells me, “it is for sure the alternator, without a doubt”. I just pulled the alternator, it seems perfectly fine. There is absolutely no play in the output shaft, no noise when I spin it. The bolt that holds the couple gear in is tight, but there is a little, very little, play in the coupler gear. It doesn’t feel like enough play to make the loud rattling noise I am hearing. Before I shell out hundreds more throwing new parts at this mysterious rattling problem, which I am now positive the dealership is incompetent about troubleshooting, does anyone here have any suggestions on what to check next?

Thanks!

[nickbw]

AOC pully is on-the-way-out, change it before the alternator belt brakes, tangles in the timing belt and takes out the engine.

[Capndirk]

There's no timing belt on that engine. I wonder if he got it sorted? The post was from 2018.

[amonti]

There's no timing belt on that engine. I wonder if he got it sorted? The post was from 2018.

I was wondering that myself - my previous BMW 535i had an issue (on every car with that engine) where the oil filter mount gasket seeped oil which ran down the front of the engine and softened the accessory belt. When the belt finally gave out, it would tend to shred and be 'sucked' into the main engine bearing.