2001 xterra brake problem (brake booster vacuum?)

[runethechamp]

My wife has a 2001 Xterra, 4wd, AT, V6 engine and it developed a brake problem just recently. First I would notice that there was a hissing sound coming from somewhere close to the brake pedal (brake booster I guess) whenever I would pushe the brake pedal hard. This other day I realized I can push the brake pedal all the way to the floor without getting full brake power. I assume these two are related.

The pedal doesn't seem to be spongy so I don't think I have air in the brake lines. I have no idea how the air would have gotten there in any case since I've never opened those up. And, if I keep my foot on the pedal after I stop the car, the pedal comes up supstantially after a couple of seconds. Is that normal?

I am thinking there is a vacuum leak or some vacuum related thing going on around the brake booster. Does anyone have an idea about what this can be?

[runethechamp]

Anyone???

[Ramius83]

There is a diaphram inside the brake booster that the engine vacuum acts on to "pull" the pedal when you apply the brake pedal. By the sounds of it, this diaphram has ruptured, thus, creating a vacuum leak and thusmore, causing a loss of brake assistance. This will NOT create a problem with air entering the brake lines as they are dealing with different components of the brake system. However, you will need to replace the brake booster to remedy this problem as this diaphram is a non-serviceable part of the brake booster.