99 stratus making funny noise

i brought it to the mechanic, we spent all morning taking stuff apart and putting it back together. it sounds like a tapping/ grinding, we thought it was the timing belt, or a tensioner. but it wasnt. we thought maybe water pump but it was nt. it is a 99 stratus witha 2.4 l 4 cyl. if anyone knows what its is would be a great help

Any way to put some audio of it on here?

When does it happen? driving? all the time?

I have had to replace the fan belt Idler Pulley on mine a couple of times. They wear out pretty quick. It starts off as a low whining noise, and as it wears worse it becomes a loud whine, sometimes with a slight grinding noise. They are inexpensive, but if you replace this, I would recommend getting it from the dealer. All the aftermarket pulleys I have tried don't fit correctly on the engine, and have taken them all back just to get the one from the dealer. They are only about $20 at the dealer.