Spongy CX-9 Pedals Because of Brake Booster Failure

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#brakes #investigation #warranty
CX-9 brake pedal replaced with a sponge

There is no more important safety feature in your car than the brakes. Yes, teenage drivers -- that's even more important than bluetooth connectivity. Unfortunately, owners of the 2010-2011 CX-9 have been having problems bringing their car to a stop.

The Brake Symptoms

CX-9 owners, especially those in hotter climates, have been telling harrowing tales of brake problems centered around:

  • A possible loss of power assist making the brakes really hard to push at times
  • A sudden loss of braking ability with super spongy pedals
  • A strange, hissing noise coming from the pedal area

All signs pointed to a faulty brake booster, prompting a government investigation in February, 2014.

The Brake Investigation

The National Highway Traffic Safety Administration (NHTSA) centered their investigation on 62,000 model year 2010-2011 CX-9 vehicles. Sure enough, those cars were experiencing brake issues but before the investigation could continue, Mazda announced their had identified the problem.

Mazda narrowed the problem to a materials issue in the brake booster, specifically:

  • The brake booster diaphragms develop tears near the outer seal that can result in noise and degraded performance as the tears grow
  • The tears allow leakage "from the ambient to the vacuum sides of the diaphragm" which reduces the differential pressure and produces a hissing noise after the tears "reach 10-12mm in length".
  • The problem was caused but a wear of the mold used during the diaphragm forming process.
  • Because of the manufacturing defect, high temperatures could accelerate the hardening of the diaphragm, further increasing stress on the area and leading to those tears

Additionally, Mazda found that drivers were having a hard time pushing the pedal during "initial pedal application", but that effort diminished as the pedal was pressed further and the tear is partially sealed by the outer wall of the booster. This sudden change explains why some drivers felt the pedal turned "spongy."

Mazda decided to extend their warranty (details below) which satisfied NHTSA, who closed their investigation in July, 2014.

The Extended Brake Warranty

Calling it a "special service program", Mazda agreed to extend the warranty coverage for this brake issue into two separate actions:

  • For repairs done between 03/31/2014 and 03/31/2015: warranty coverage will be extended for an unlimited time and mileage for owners who receive brake repairs in this time period
  • For repairs done after 03/31/2015: owners will receive an extended warranty if 7 years or 90,000 miles

Clearly, if you're having brake problems you'll want to get them fixed before the end of March, 2015. Call Mazda at 800-222-5500 with any questions.

Mazda brake image via Mr. TinDC on Flickr

Generations Where This Problem Has Been Reported

This problem has popped up in the following Mazda generations.

Most years within a generation share the same parts and manufacturing process. You can also expect them to share the same problems. So while it may not be a problem in every year yet, it's worth looking out for.

Further Reading

A timeline of stories related to this problem. We try to boil these stories down to the most important bits so you can quickly see where things stand. Interested in getting these stories in an email? Signup for free email alerts for your vehicle over at CarComplaints.com.

OK, Now What?

Maybe you've experienced this problem. Maybe you're concerned you will soon. Whatever the reason, here's a handful of things you can do to make sure it gets the attention it deserves.

  1. File Your Complaint

    CarComplaints.com is a free site dedicated to uncovering problem trends and informing owners about potential issues with their cars. Major class action law firms use this data when researching cases.

    Add a Complaint
  2. Notify CAS

    The Center for Auto Safety (CAS) is a pro-consumer organization that researches auto safety issues & often compels the US government to do the right thing through lobbying & lawsuits.

    Notify The CAS
  3. Report a Safety Concern

    The National Highway Traffic Safety Administration (NHTSA) is the US agency with the authority to conduct vehicle defect investigations & force recalls. Their focus is on safety-related issues.

    Report to NHTSA