Hello, just brought a used 2014 cx9 and experienced brake failure. Seems there is a recurring issue since 2010 with the break booster. Breaks start making a hissing noise then require full force to come to a stop. Very dangerous situation. We are having it replaced but this is something that is happening to a lot of owners from what I have researched. Can anyone tell me if the booster eventually fails, and it is replaced, are they just replacing with the same part, that will in turn eventually fail again, or have they re-engineered the part so it is a real fix. Most cars end up with this problem first happening at 35 to 50k miles. Ours was at 44k.

 

I have a 2014 CX-9 with 44,000 miles and just experienced the same thing. My brakes appeared to be working just fine during a 40 minute drive to a destination. When attempting to leave the parking lot of the destination, I backed out of the parking spot and my brake pedal almost went to the floor and took longer than usual to stop. When I put it in gear, I drove very slow and applied the brakes again and the pedal did the exact same thing. I put on my emergency flashers and carefully parked into an empty space and called roadside assistance. While I was waiting, with my car in Park, I pressed the brakes and they went to the floor and made an unusual sound. I never had any problems with my brakes before this. As a matter of fact I just had it serviced in July of 2017 and had the brake system flushed.
After towing to the dealership, it took them awhile to figure out what was wrong. When they did, they told me the "ABS module" was bad and that I needed a new one at $1670.00 and that the part would not be available until Monday (7 days). Had this happened during my commute back on the expressway, I'm not sure this would have ended in a good way.