I hate to beat an old thread, but I am having a somewhat similar issue with my 04 XE... Rear brakes are not working on it. Checked all lines, no leaks, not loosing fluid, and no contamination of gear lube from axle. I have bleed the system until I got fresh fluid coming out all 4 calipers, and no air was found in the system. I haven't been able to find an answer to this issue, and was hoping someone here might know a solution. Here are the facts below:
Brake Pedal: Spongy (Goes to the floor if slammed) and if normal stopping, goes about 3/4 way to floor and soft.
Front Brake Pads: Last about 3-4 months (average 1.5k miles per month).
Front Rotors: Constantly having to machine when changing pads, due to severe warping and pedal pulsing
Rear Brake Pads: 4 years old and no sign of wear except a few scratches, and only 12 thousands thinner than new.
Rear Rotors: Had machines but no sign of useage since last machining (going off the machine marks still visable on rotors).
E-Brake: Works fine.
Brake Lines: No apparent leaks, no air in system, and fresh fluid throughout system.
Dealer Update: Master Cylinder, Booster, and ABS system have been checked and all fine. Nissan is saying it's normal, but never heard of any vehicle never using the rear brakes.
Any help would be greatly appreciated, as this has been going on for 3 years, and have yet to find any information on why the rear brakes are not working.
**I know the rear lines aren't clogged, as fluid comes out the bleeder valve when the brake pedal is depressed.