It always happens first thing in the morning, and various times throughout the day.
When braking(in reverse), there is a squeal.
I first replaced the pads on all four wheels. No luck.
I then took it in to service. They turned the rear rotors and also replaced the rear pads. The squeal is still there.
What other possibilities could be causing this?

Thanks

 

My 2012 does this often, I just ignore it, the brakes work fine and have tons of pad/rotor left.

 

dad004, what year is your CX-9?

 

The squeal is metal on metal rubbing. It is the steel pad backing plate rubbing against the cast iron caliper. Remove the pads and the calipers and look closely at the caliper's high points that contact the pad backing plate. You'll see shiny spots. Any auto parts store sells several products to lube these spots or rubbery spray to damp vibrations. Some brands of pads include separate anti-squeal shims. Try one of the anti-squeal products. If there are new clips or shims for your brakes, and you used the old ones, get the new ones. If one brand of goop stops the squeal long-term, great. If not, try something else.

Certain brands of pads may squeal more than others. Pad friction material deposits on the rotors may cause a stick-slip-stick-slip at very high frequency and squeal. Resurfacing the rotors removes the deposits, as would sanding with emery cloth and washing with brake clean solvent. You've covered those bases. Go for the anti-squeal products now.

Did your work order at the repair shop specifically say that the rears were squealing? If so, take it back and get them to fix it right without extra charge. If not, next time don't sign the order until they include the problem as well as the service writer's guess as what it'll take to fix it. No fix-no pay. Take it back anyway...new squealing brakes is not a job done well. Don't let them sell you new rotors...they'll keep selling you parts until they stumble across what will really fix it.

 

This has never let me down.....