Brake Power Boost Unit Failure

2012 Mazda CX-9 (Page 2 of 2)

This problem may be covered under warranty. Ask your Mazda dealer. Seal Of This Might Hurt Notes: The only area of real concern for 2012 Mazda CX-9 owners is the brake booster.

In 2014, Mazda extended the warranty on the 2007-2013 CX-9 brake booster to 7 years / 90,000 miles. However this extended warranty has expired for most CX-9 owners, so buyer beware.

This Mazda CX-9 brake booster failure isn't terrible in terms of repair cost — it "only" costs $550 average to fix. However it is a safety issue when the brake booster fails as it increases stopping distance. Owners have reported having to stomp on the brake pedal, & crashes/injuries have been reported due to this CX-9 brake booster defect.


pretty bad
Typical Repair Cost:
Average Mileage:
67,800 miles
Total Complaints:
27 complaints

Most Common Solutions:

  1. replaced by dealership (10 reports)
  2. not sure (9 reports)
  3. replace brake booster (7 reports)
  4. too soon to tell (1 reports)
2012 Mazda CX-9 brakes problems

brakes problem

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2012 Mazda CX-9 Owner Comments (Page 2 of 2)

« Read the previous 20 complaints

problem #7

Apr 152016

CX-9 3.7L

  • Automatic transmission
  • 60,000 miles


Progressively worse. My 1st Mazda. At first I thought it was something I needed to accept but it now lurches forward at times when I was already at a stop.I have started putting it in Neutral at stops. Weird whining noise if you continue to push down on pedal.

- William P., Columbia, SC, US

problem #6

May 062016


  • Automatic transmission
  • 62,133 miles

The brakes have become very hard when trying to apply for a stop. It feels like car is now going to stop in time, I had to switch to Manual Transmission (luckily car has this feature) in order to get home, using down shifting technique. Very Scary.

- gordo517, Long Beach, NY, US

problem #5

Mar 152016


  • Automatic transmission
  • 41,680 miles

The brakes have become very difficult to push. They slow down the car, but require intense pressure to bring the vehicle to a complete stop. There is also a slight hissing noise when the brakes are applied. It takes about twice the distance to come to a complete stop than previously. There is no indication of a problem on the dashboard; no warning light has been displaying, but something is definitely wrong. I do not feel very safe when driving.

- bmellor, Erda, UT, US

problem #4

Feb 222016

CX-9 Touring 3.7L V6

  • Automatic transmission
  • 19,263 miles


This brake problem has apparently already been identified and resolved for 2010 - 2011 Mazda CX9 - see the following link: [], but there was no mention of my model year (2012). I discovered this information, on your website, before I went to the Mazda dealer in Edmonton about the brake problem.

Symptoms of the brake problem included: loss of power assist making the brakes really hard to push at times: and, hissing noise coming from behind the dashboard area. The problem with my car started about 2 or 3 weeks before going to the dealership and the "hard pedal" was only occurring during very slow speed parking maneuvers. I printed out the information from the web page, showed the dealer, on March 11, 2016, and explained that my brake problem was exactly as described on your website.

The service people at the dealership told me that they had never heard of this problem and were skeptical that I had accurately diagnosed the problem by simply reading about it on your website. The dealer checked the car and confirmed brake booster failure is the problem, and told me that the car is unsafe to drive. The replacement part has to be shipped from Vancouver BC and I have an appointment on Tuesday March 15th for the work to be done.

I have a concern that, according to the information I read on your website the NHTSA thinks this problem was limited to the 2010 and 2011 model years. Therefore NHTSA, Mazda, Mazda dealers, and 2012 CX9 owners should all be notified that the problem is occurring with 2012 models as well!

- risingson, Edmonton, AB, Canada

problem #3

Dec 192013

CX-9 GT 3.7L

  • Automatic transmission
  • 932 miles

Mazda CX- 9 2012 model I purchased on Nov-26-2013 from show room here in Qatar. From the day I have lots complaints in my car. I am complaining about my car to the show room manger and the service engineer and they just make its a silly issues. After a week my car stuck over road several times and they took into the service that is BRAKE POWER BOOST UNIT FAILURE. This I know only after 8 months when I got the service history of my car. They replaced it without saying anything. I ask about the complaints they say just jammed. After one week my car can't start. Again I call them for assist, it took one week again to get them respond about my compliant and they replace the battery and starter.

Another problem with power window motor I can't open and close the both front windows. I inform them they said we will see in next service. After only 5000km I used my car my brake pad and disc got damaged. They say I am a rash driver, that's why brake pad damaged, I replaced it . Before another 5000km I can't use my car because disc and brake pad damaged again. I can't move my car. I ask them service history of my car, they refuse to give me because recently some of other car brands showrooms closed here in Qatar by consumer court because of violations of consumer law. I hope I will get any contact details for Mazda through here better than contact dealer here in Qatar hopefully.

**please ignore any mistakes here I make. Thank you.

- harmon123, Doha`, Qatar

problem #2

May 072015

CX-9 Grand Touring 3.7L V6

  • Automatic transmission
  • 40,550 miles

Over the course of several days, the brake pedal didn't feel normal or it required more pressure to stop the car. The problem was intermittent and I thought it might just be me. Then I was sitting in a drive-thru and the a/c kicked on or off causing the revs to rise and I lunged forward almost hitting the car ahead of me. I knew that I had a problem at that point.

After some research online, I determined that the brake booster was the most likely culprit. The following Monday, I took it to the dealership and told them what it was doing and that I felt the brake booster was the issue. The service writer explained that Mazda had extended the warranty on the brake booster beyond the basic 3-year/36k mile warranty. Since I was 4550 miles over the 36k limit, I was glad to hear that.

It took four days for them to get the part and perform the repair, but they gave me a loaner to drive. Overall, I still love the vehicle and have had no other troubles since it was new. My only concern is that Mazda hasn't performed a recall on the CX-9s affected (which would cost them a lot more) rather than simply covering the ones that fail under warranty. The potential for an accident is very high for someone when the brake booster fails, especially if the driver needs to stop very quickly or lacks the physical strength to apply a LOT of extra pressure to the brake pedal.

- igozoom, Waleska, GA, US

problem #1

Nov 192014

CX-9 Touring 3.7L V6

  • Automatic transmission
  • 45,000 miles

Excellent car!!! No issues accept the bad Brake Power Boost Unit that was replaced under warranty. Acceleration is great, the ride is a true pleasure. Though many convenience additions are absent (e.g. power liftgate, automatic folding mirrors, memory seats, tire pressure sensors) the car is built very well. Comfortable heated front seats (both electrically powered), good noise isolation, pleasant leather upholstery, a lot of cargo space with the 3rd row folded, rear a/c, sliding 2nd row!

Love the car!

- guygo, San Diego, Ca, US

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