Which parts fail
Components named in complaints (service brakes, ABS, rotors and pads, parking brake).
Mileage when the problem started
Owner reports
Selected complaints filed with NHTSA by 2012 Mazda CX-9 owners, lightly cleaned up (personal details are redacted by NHTSA).
The contact owns a 2012 Mazda CX-9. The contact stated while driving 25 mph and approaching a stop sign, depressing the brake pedal the vehicle failed to stop. The contact stated that there was no warning light illuminated. The contact stated that she pumped the brake pedal and shifted to neutral until the vehicle came to a stop. The contact was able to drive to her residence. The contact took the vehicle to an independent mechanic and was informed that the power brake booster and master cylinder needed to be replaced. The vehicle was repaired. A dealer was not contacted. The manufacturer was informed of the failure. The failure mileage was 29,805.
This is relating to NHTSA Investigation PE 14-005. Although this car is a 2012 Mazda CX9, my wife driving the car had the same issue where she heard a hissing noise and the brakes were very difficult for her to depress or to stop. A brake issue is a major defect where the NHTSA should have initiated a recall in accordance with 49 U.S.C. 30118-30120, which required notification of all owners. Why the NHTSA allowed Mazda to only issue a 'Special Extended Warranty' is beyond me, and smells of a back door deal. Nonetheless, I was unaware of this issue with the Mazda CX9's as I was never notified. My wife drove the vehicle home and I purchased the replacement parts at my own expense. This should be a full recall and should be reopened as your current investigation PE 14-005 only included years 2010-2011, and did *not* include the 2012 model year.
I was driving normally when I started sowing down and noticed the brakes were harder to push. I finally stopped just before almost rear-ending a vehicle in front of me. It turns out the brake booster, a known problem that was not communicated to me a few years ago, failed and makes braking the vehicle harder, increases distance, and makes the vehicle unsafe to drive. The problem has been reproduced via a diagnostic test at Mazda of Gladstone dealership on 9/27/23. The dealership has been the only people who have inspected the issue. There were no warning signs, no warning lights, nothing. It was scary because I didn't think my vehicle was going to stop. It's completely dangerous. I have not gotten the vehicle repaired yet because I believe Mazda holds responsibility as this has been a known issue with their cars.
On August 14, 2020, the brake booster along with the master cylinder failed, resulting in very dangerous and frightening driving conditions, and the parts were replaced with Mazda original parts. This was an ongoing issue with the Mazda CX-9's. I reported it to the NHTSA, complaint number 11480067. On January 4, 2023, the brake master cylinder and booster failed again resulting again in very dangerous and frightening driving conditions. The car was driven only 25,383 miles before the brakes failed the second time. The Mazda parts were defective and continue to be so after many years with no effort by Mazda to improve these parts. Attached are the repair invoices for both incidents. I have tried contacting Mazda and they refuse to address the issue.
The brakes suddenly became very difficult to press as if I did not have power brakes. No warning lights came on and it became very difficult to stop the car. Then if I had to break suddenly and hard it would stall. I brought it to the repair shop and the brake booster was defective. The brake booster along with the master cylinder had to be replaced. It was a very dangerous and frightening experience the brakes suddenly difficult to use. I contacted Mazda customer service and they did not care. I then tried to escalate the issue over the last two years but it was impossible to contact anyone and all emails came back undeliverable. I just recently learned that I can report this danger to the NHTSA.
Brake booster failure caused a near miss. Wife driving with 5 year old daughter in the vehicle. The stopping force required on the brake pedal became excessive and the stopping (safe braking) distance significantly increased causing emotional distress. My understanding is this part (brake booster) has a defective diaphragm that deteriorates over time. The extended warranty created for this particular issue did not cover the vehicle at the time of the failure.
I was driving along the highway and traffic began to slow. I pushed the brakes and the car did not stop.
The braking system did not function correctly resulting in a crash. Brakes were hard and could not be depressed when a vehicle stopped quickly in front of me. Took the car to Mazda dealership and they informed me that this is a known problem and replaced the brake booster under a "special warranty". This needs to be a safety recall, I was never notified of this safety issue. It is imperative that nhtsb reopen the investigation on this problem as it does not only involve 2010 and 2011 cars and does not only occur in "high ambient temperatures". Vehicle was in motion and was slowing on an slight uphill grade. Vehicle is 5 years old and has 53,000 miles.
I've purchased 2012 Mazda CX-9 AWD it late November of 2011.recently I've been experiencing multiple unexpected loss of power-assisted brakes failure incident .I was in a minor fender bendeer. Thank god the driver infront was very nice and didnt file any claim against my insurance. When I brought my vehicle into Mazda services department to get it resolve. Instead of taking unexpected loss of power-assisted brakes as an urgent matter. They told me that my car is drivable and it still break. I can drive my Mazda in the meanwhile, until they have an open appointment for my Mazda to be seen. After speaking to multiple personel at the services department. They were able to take my Mazda and fixed the unexpected loss of power-assisted brakes. Now im experiencing speed control and power train. …
I reversed my vehicle into a parking spot and started hearing abnormal noise like brakes grinding, but was still present even when not moving. Having a car backround I knew it was more like air. Wasn't sure what it was, but because I already work at a dealership I decided to have one of my diagnostic techs check it out. He knew right from my description that it was probably brake booster related. Called my dealership that always services my car for an emergency drop off. Bringing the vehicle to the dealership, every time I braked the pedal would not go down all the way, go straight to the floor, or I'd have to double tap the brakes similiar to if I was driving on ice. When at stops I'd hear the air noise from the booster, and even when the vehicle was off the pedal goes to the floor. …
Brake complaints in other CX-9 years
Frequently asked questions
How common are brake problems on the 2012 Mazda CX-9?
NHTSA has 143 complaints about the brakes of the 2012 Mazda CX-9, 65% of the model year's 221 complaints. The component named most often is pedals and linkages (1 mentions).
Is there a recall for 2012 Mazda CX-9 brake problems?
No. NHTSA lists no brakes recall for the 2012 Mazda CX-9, though it has 4 recalls for other components. If the problem is widespread, a repair may still be covered by an extended warranty or a manufacturer service bulletin — ask a dealer.
At what mileage do 2012 Mazda CX-9 brake problems start?
Half of the complaints with a recorded mileage happened before about 57,000 miles, and 11% before 25,000 miles.
Is it dangerous?
Owners linked 4 crashes, 0 fires and 1 injury to brakes problems on this model year. If you notice symptoms, have the car checked before driving further.
Source: U.S. National Highway Traffic Safety Administration (NHTSA) — owner complaints through October 20, 2026, recalls and defect investigations; fuel economy from the EPA. Complaints are unverified reports and are not proof of a defect. How we rate model years.