 Mazda is having an issue with brake boosters in the CX-9.  Mine failed today at 52K miles.  I couldn't stop the car pulling out of the garage and rolled it into my side yard.  I took it into the Mazda dealership, and they know there's an issue.  There's a service bulletin, and they replace the brake booster for free.  I can't believe they haven't recalled the car - this could cause a serious accident.There is an issue with the diaphragm in the brake booster failing in hot climates.  I live in Ohio.  It can get hot here, but give me a "brake" - literally.  The dealership cannot tell me if the new brake booster has the same issue.  I'm assuming it does since I've read about these failures happening in the CX-9 since this design was released.  The car is at the dealership every 5K miles for maintenance - they didn't catch it there either.  You'd think they would check since it's a recurring issue.I'm beyond disappointed Mazda allows the car to be on the road with this type of failure possible.  I wouldn't buy this car again.