I've had my 2009 Mazda6 for almost a year now and its produced the subject problem ever since. With the A/C on or off, there is a squealing noise that comes from under the hood whenever the car is idle while in drive gear. Every time I take it to my Mazda dealership for the routine inspection and oil change, they never seem to find what's going on. I'm getting tired of them not finding what the problem is and I would gladly fix it myself if it's as easy as applying grease somewhere. Has anyone had this issue before and if so, how did you get around it? Thanks in advance!

 

Loose drive belt? Bad belt tensioner? Bad drive pulley? All likely culprits... Sounds like your mechanic isn't looking too hard.

 

Ok, first off, unless your dealership is doing the stuff for free, stop taking it to them. They will overcharge for EVERYTHING. Find a reputable 3rd party mechanic and take it to them, see if they can find the problem. And Soylents suggestions were all right on the money for what I'd suggest you have checked, starting with the belt.

 

This is a known issue on the 2009 Mazda 6. The sound is coming from the exhaust pipe underneath. There is a spot where 2 pipes connect and there is a design flaw where the connecting bolt(s) is rubbing up against metal during vibration of the engine. Take it to a dealer hopefully you're still under warranty and if they can't find it tell them to look at the maintenance bulletins for what I just described. They just came out with a solution a few days ago and they should take care of it for no charge if you are still under warranty. Let me know how it goes. Good luck.

 

Will do, jchen2007! I had just about given up on this but I'll be sure to add it to the list before the three years are up in the next month or so. Thanks!