No brakes (at all!) but why?

[20maxima00]

About three weeks ago, my wife came home in her 2000 Nissan Maxima and told me that the "BRAKE" light was on on her dashboard. I told her that she needed to make sure the emergency brake was all the way down and that should turn it off. If it did not, then there may be something else wrong. When she didn't bring it up again, I assumed she just left the emergency brake slightly up.

I was wrong.

After riding with the BRAKE light on for three weeks, her brakes suddenly went completely out one morning. I thought she was exaggerating, but I got in the car, put it in drive (with NO gas) and could not stop the car - not with the emergency brake or regular brakes. I had to just flip it into park for a sudden stop (only went three feet at half a mile an hour, but still).

I checked the brake fluid and it was almost completely out, so I went out and bought the stuff I needed (DOT 3) and filled her up just below the MAX line.

Still no brakes. None at all.

I have her press the brakes with the car on but in park and none of them are clamping down on the wheels. The brake fluid is disappearing at an alarming rate from the container that holds it, though.

I assume there is a leak somewhere along the line, and a massive one at that.

I throw some paper underneath the car to catch the drip and have her press the brakes. First with the car off, then with the car on but in park.

No drips anywhere. There was nothing on the paper underneath the car and there was nothing on the wheels, either.

I wait a few minutes and look under the he hood again..... and the brake fluid has "returned" to the container back up to the original line. It had dropped over an inch while we were pressing the brakes constantly.

I was tempted to junk the car even before this, but want to make sure it's not something totally obvious (and inexpensive) that I may be missing here. Thoughts?

Any and all help is appreciated. Thank you very much.

[Keen240sx]

Possibly the master cylinder, however the e-brake is on a cable so that should always work unless that is just not by conincidence connected properly. A lot of places offer free quotes but I imagine getting it there would be a problem... There's no for sure way to tell but I would do some research on that master. How are the calipers etc...?

[maxhopper]

If there are no leaks visible from the lines or the calipers, I would have to agree on the master cylinder being the most likely cause.

[20maxima00]

Mechanic says master cylinder is fine and he could find no leaks.

He bled the brakes and they work again, but tried to tell me that there was no air in the system.

He blames it all on the brakes just being "real bad." Thinking I need to find a new mechanic.