My swamp (evaporative) cooler makes noises after it has been run a week or so every year. A buzzing noise. I can quiet it by pressing firmly on the front inside grill/panel towards the bottom. I tried adding soft washers under the four corner screws fastening this grill last year but it didn't help. I'm not sure whether the grill is causing the noise because it has a mounting problem or, more likely, the blower is vibrating and causing it to buzz. Just yesterday I tried lubing the blower bearings again (after prepping it for the summer a month or two ago) but no help. I can't see anything obvious causing the problem. The belt looks ok. This cooler is only a few years old - third season I think, maybe fourth.
Can anyone give me any ideas on how to chase this down?
TIA