Six problems related to brake master cylinder have been reported for the 2011 Mazda CX9. The most recently reported issues are listed below.
Brake master cylinder hissing and squealing while engine is in idle. After revving (and releasing) to 2000 rpm's and applying (holding) brake pressure simultaneously, the build up vacuum pressure does not allow engine to return to idle rpm. Rpm hangs at 1500 rpm's. If vehicle is in drive while accomplishing this then the brake pressure applied is not enough to bring the vehicle to a stop. After find the cause of the issue I went online and found previous message boards about this issued were posted in early 2014 but a recall was never issued. Reported the issue to Mazda (20161012) but was told that since the vehicle is 30k outside of the extended warranty then the issue belongs to the consumer. (mazdaref 1-368-227-539).
Hissing sound when applying brakes, brake feels stiff. Have an appointment tomorrow (they said it should be ok to drive until then), said it was probably the master cylinder failing.
When pressing the brakes at any speed there was a hissing sound and the brakes were hard to press. Regardless of the amount of pressure I applied to the brakes they did not react and it took the vehicle longer to slow down even at very low speeds (5-10 mph) or faster. This came on suddenly and caused me to bring the vehicle into the service department of the the dealership where I purchased it. The Mazda technician inspected the vehicles and completed a diagnostics of the vehicle and discovered that the master cylinder and brake booster have failed and need to be replaced.
I actually noticed when I started my vehicle up and pressed on the brake pedal, it seemed to slowly sink all the way to the floor and made a hissing noise. The noise only stopped when I took my foot off the brake pedal. As I was driving, on several occasions I had dramatically reduced stopping performance when applying the brake. I've gone through several stop signs and have almost rear ended other vehicles. This seems to have suddenly happened, I first noticed it on 3/1/15. This wasn't happening on or before 2/26/15. I suspect the power booster or master cylinder have failed, though I'm concerned that this happened with only 61,000 miles on it.
My wife complained that the brakes didn't seem to be stopping the vehicle very well. I drove the car and almost had an accident. At slow speed the brake pedal was very hard to depress and made a hissing sound, but continued to travel slowly toward the floor. I limped it to the Mazda dealer and I was told that the booster and master cylinder needed to be replaced. When I questioned the service manager about Mazda's problems with cx-9 brakes, he said mine was the first one he had heard of. I drove away as fast, carefully and safely as I could.
Similar to other complaints here, I recently started noticing hissing when I pressed my brakes. . . . . . . I noticed that I was having a hard time coming to a complete stop. I took my Cx9 in today August 14, 2013 to gunther Mazda in fort lauderdale. I thought it was going to be a simple change of brake pads, little did I know I was in for $700!!!!!- apparently this is nothing new for Mazda, there was an investigation going on by the NHTSA for the 2008 Cx9 model and guess what? the 2011 seems to be having the same exact issue. The mechanic said the pads are fine but the master cylinder and booster need to be replaced. I'm going to call Mazda USA to see what they can do but unless everyone starts demanding answers they're going to be laughing all the way to the bank. It'll take a strong effort to make them issue a recall. This is my last Mazda. I'm going back to my Lexus, more expensive by a lot but I didn't have to worry about putting my life and my daughter's life at risk. This is ridiculous.