While traveling on the highway rush hour traffic my brakes started malfunctioning. The traffic ahead of my vehicle came to a sudden halt. I applied my brakes (100 ft. From collision), however, they failed to decelerate the vehicle- it didn't feel as though I had applied them. In order to prevent a collision I depressed the peddle with all of my strength (60 ft. From collision). Gradually, and insufficiently, the car began to decelerate. With the brake peddle fully depressed. Suddenly (25 ft. From collision) the brakes tightly grasped the rotor and the tires screeched- thrusting the passenger and I forward. Then the braked released and grasped again.the vehicle finally stopped inches short of a collision with the ahead of mine. For the past few days, the car has continued to exhibit similar symptoms. When I fully depress the break the vehicle makes a hissing sound and the rpms drop- on one occasion this action caused the cuv to shut off. I have to remain an additional 50 ft. Behind other vehicles in order to insure that I have sufficient time to stop.

- Crowley, TX, USA

The brakes on the vehicle have become unpredictable. I initially took the car to my local shop only to be turned around being told that there was not enough wear on the pads to warrant replacement and that everything looked fine. However, being the owner of the car, I can confirm a severe and sudden regression in the breaking behavior. While the car still slows down when the breaks are applied, the pedal has become very hard and the ability to stop suddenly is severely comprised (even at a slow speed). I have to plan my braking point much further away from my anticipated stopping point which makes driving much trickier. I would not trust the vehicle to save me from a crash were I to require emergency braking.

- Belmont, CA, USA

I was driving in my Mazda 2011 CX9 SUV when I pressed on the brakes and they would not engage. I had to press repeatedly, extremely hard in order to get the vehicle to stop. I have taken the car into my Mazda dealer who is saying that I have a problem with the master cylinder leaking fluid into the booster. Mazda has not sent a recall for the master cylinder only for the booster. This is a very dangerous situation and one that needs to be addressed before someone gets into an accident. This car is 2.5 years old and has 42000 miles and should not be having these problems. Mazda needs to honor the repair and fix this problem.

- Pembroke Pines, FL, USA

Brakes failed to engage 3 times this morning, the first time failed to stop the SUV so had to swerve to the center median and slightly hit the metal barrier. Then going back home making a turn, brakes failed again to engage. Seems this happened when making turns. Brought to the Mazda dealer, told them about ongoing investigation by NHTSA about Mazda CX9 2010-2011 brake problems. They did a thorough check but could not duplicate the problem so nothing was fixed. It might be the brake booster. I'm afraid this might happen again, they said there was no recall regarding brakes for 2011 Mazda CX9. Hope that NHTSA forces Mazda to make a recall. Mazda has to fix this dangerous problem.

- Holbrook, NY, USA

Our 2011 cx 9 brakes are failing. The power brake booster will at times not work making the brakes very hard to depress and without the ability to quickly and safely stop the car.

- Bellevue , ID, USA

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.

- Floyds Knobs, IN, USA

I have not had a accident yet, however since I purchased the car new I have had trouble with the front brakes, especially the right wheel. The dealer say there is nothing wrong and I have complained about this issue several times at regular service. I know something is wrong, the pedal fades and there is a grinding and sometimes hissing noise from the front right. It needs to be corrected by the dealer before something really bad happens.

- Los Angeles, CA, USA

I was driving to the grocery store with my two year old and my seven year old. When I applied my brakes at a stoplight my car did not slow down until I put both feet on the brake peddle and push with all my might. There was no warning light for a brake problem. The car was making a high pitch screaming noise when I applied the brake. My father who is an engineer check the car and found the brake fluid low and it had leaked into the booster and ruined it. I looked on line and found several Mazda owners had reported the same problem. My family, I and anyone else on the road lives are in danger if this is not recalled and corrected immediately.

- Ellenton, FL, USA

Brake pedal became increasing hard to depress requiring an excessive amount of force to engage brakes. Stopping power decreased and distance to a full stop increased leading to very dangerous situations when driving the vehicle. Mechanic says the brake booster needs to be replaced.

- Martinez, CA, USA

I was driving my son to the doctors office when I realized the brakes did not feel right. I told my husband that I felt a lot of resistance when applying the brakes. So when I got home I had my husband drive the car and he said he did not feel anything until later that night when he was driving the vehicle he freaked out cause he said he felt as if the car wasn't going to stop after pushing on the brakes. He had to pull off of the highway and take the back roads home at a low speed and give himself plenty of distance from the car in front of him in order to brake so he would not slam into their car. Also, when applying all the pressure you could to the brakes, a loud hissing sound could be heard as well. The car was taken to our Mazda dealer where the car was purchased and after they looked at it, we were told that the vehicle had bad brake boosters and that we were lucky we weren't in an accident. After hearing this and researching it, it really upset us that Mazda has had this issue with the same model vehicle of other years.... why hasn't a recall been done" are they waiting for someone to lose their life before something is done"! I thank god we were able to stop our car but there was no warning or lead up to this incident. It literally just happened out of nowhere!

- Corpus Christi, TX, USA

August 6th 2013 my wife complained about the brakes on her 2011 Mazda CX9 making a hissing type sound and brakes feeling mushy and not responding as normal. The next day she advised the brakes were worse so we parked the car until the 9th. The CX9 has 46000. Miles. The car receives regular maintenance and was taken to tom bush Mazda (jacksonville fl.) for diagnosis of the problem. We were advised that the issue was a vacuum leak from the brake booster and it had to be repaired at the cost of $695.88. (part = $130. W/ labor $503.) we learned that others have had the same problem and that a recall might have been issued for the previous year cx9S. There was no consideration on repair costs. Our issue is the brake vacuum booster failure seems to be an abnormally common complaint on Mazda's CX9 vehicles and the fact that this involves brake failures, is a safety issue that may lead to a catastrophic crash at higher speeds. I believe other similar complaints noted about Mazda CX9 brake issues in the NHTSA warrant a thorough investigation and possible recall. We will retain the defective part. Further note, the Mazda dealership released the vehicle to my father w/O properly inspecting their work. The vehicle was released to us w/O the brake lines being bled properly which caused the brakes to fail while at the dealership. It took another day to fix that issue.

- Jacksonville, FL, USA

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.

- Weston, FL, USA

I just stated noticing issues with my brakes, I started hearing a low hissing noise and noticed that I was having a hard time coming to a complete stop. I need to pump the brakes several times to slow down and then once stopped the brakes go all the way to the floor. I took my CX9 in today July 8, 2013 to have the brakes checked and the oil changed. I was told the breaks and pads are fine but there is something wrong with the brakes. They tried flushing the lines and that did not help. They told me they could not look at the car further until Wednesday July 10th. I asked if the car was safe to drive they said it was and to go slowly upon reaching a light and make sure to pump the breaks so I can stop in time and not go through the intersection. This is very alarming to me since an accident can occur this is my only vehicle and I need to get back and forth to work. They told me they needed to call the Mazda help line to find out what is wrong with the breaks. After researching on line today Mazda CX9 brake issues am very interested to see what they say and if it is the same problem that has been reported since 2008 with this model. I am very upset since I take very good care of my car and always take it to the Mazda dealer for service. My vehicle is at the 37,000 mark which appears to be the point when this has been a problem for other vehicles. I hope that Mazda will cover the costs to fix the car and that I don't get into an accident between now and Wednesday.

- Arvada, CO, USA

Upon light braking I hear a hissing sound. The brakes are ineffective at slow speeds. It takes a longer time and requires application of greater braking force to get the car to come to a complete stop. I took the car in for inspection and am awaiting the results. I saw online that there are known problems with the braking system.

- Hermosa Beach, CA, USA

Approaching a red light on a dry sunny day, my brakes failed halfway through coming to a stop. At first my vehicle (2011 Mazda Cx-9 sport with 56,000 miles) was slowing down normally and then suddenly there was grinding/crunching noises and despite pressing the brake, the vehicle was no longer stopping. I slammed the brakes, pumped a few times, and the vehicle simply failed to slow down or stop causing me to slam into the rear of the vehicle in front of me. I took the car into a mechanic who notified me that both of my "front calipers were possibly defective, " and my front rotors were "uneven and wearing on the outside." However, my brake pads were good and did not need to be replaced. Good thing I was already stopping for the red light; therefore I estimate going about 10-15 mph (speed limit on street was 35 and I was already midway through coming to a stop at the light). Imagine if I need to brake while going 60-70 mph on the interstate! or worse, driving in the rain!

- Ft. Worth, TX, USA

Power brake booster failure.

- Peoria, AZ, USA