One problem related to brake master cylinder has been reported for the 2005 Infiniti QX56. The most recently reported issues are listed below. Please also check out the statistics and reliability analysis of the 2005 Infiniti QX56 based on all problems reported for the 2005 QX56.
Randomly, I will step on the brakes and the brakes begin to pulsate. Then it sounds like grinding sound and the brake pedal loses pressure. Almost like it hit a void and dropped to the floor. I had to try and slow down vehicle to come to a stop. Calipers and pads were all changed, per dealer findings. And it continued. I do not go over 40 mph for fear of this happening again. It's clearly and unsafe situation and the dealer claims they only hear this when people have back brakes. Guess what, I brought it to another Infiniti service center, and they said the same thing even thought the other service center replaced just about everything. Another mechanic, from the service center, took me aside and said this is frequently happening with this model and it is a master cylinder issue from design. Come on Infiniti, fix this!.