99 camaro Z28 5.7 liter V8/Auto/12,000 original miles.Theres a metallic grinding noise coming from the left side of the engine. The metallic grinding sound stops when I either put on the A/C or defogger. So to recap I hear metallic grinding noise...and when I put the A/C or defogger on I then hear the clutch engage and the metallic grinding sound goes away. It immediately comes back on when I shut the A/c or defogger off. I noticed the belt tensioner on the top left of the engine shakes. I put more tension then less tension and the noise is still there. I dont believe its the belt but its possible.Maybe a pulley is loose or needs replacement. Maybe its the tensioner pulley. I dont have any idea. Any advice? Thank you so much in advance. Please reply to cobrakillr718@yahoo.com

 

It's the AC clutch bearings. When the AC is off the clutch spins on the input shaft without turning the compressor. When it's on the clutch locks up and turns the whole shaft so the noise from the shot bearings can't be heard because it's all spinning together.
And please do not post questions on this board and expect us to e-mail you the answers. If you can post the question here you can come back and read the answers here. thanks.

 

thanks for replying. If it is the clutch bearings is this an easy fix? Would I just need to replace the bearings or get a new clutch or compressor? and did you have similar problems? Thanks

 

not cheap $$$

i do believe you need to replace the whole unit.

oh, and if the bearings get too bad they will lock up and you definantly don't want that to happen.