Firm brake pedal with engine off - vacuum leak?

[jspitz]

As the title says my brake pedal is firm without the engine running. It softens to normal within a second or two of starting the engine, and while shutting the engine off I can feel it become firm and tries to raise back up within a second or two.

Otherwise, braking behavior is normal save for a small sample of incidents where the pedal was very slightly firm when initially pressed, but felt normal by the time the pads really started to bite the rotors.

From similar symptoms online, it seems like a vacuum leak, but I can't find much in the way of Nissan- or Pathfinder-specific info.

Any thoughts? Any known failing parts?

Thanks.

[aadadams]

I'm no expert, so forgive me if I appear to oversimplify your issue... With that said, the engine's vacuum provides braking assistance through the brake booster. When the engine is off, there is no boost ergo no assistance and hard pedal. I think your brakes are functioning normally. Do you have any other symptoms..., hissing or something else that points to a vacuum leak?

[jspitz]

I may be wrong on the Pathfinder, but my memory - which admittedly could be failing me - is that the brake pedal was normally as easy (or nearly as easy) to depress with the engine off as with the engine on, at least once or so because of "stored" vacuum. Subsequent presses become firmer. Additionally, this is what my other car does, and what I remember every other power-brake equipped car doing that I have owned. A few weeks back, I hopped in the Pathy, pressed down on the brake before starting the car and immediately thought to myself, "hmmm - this is odd - the brake is much harder to depress than normal" and it has persisted ever since.

Since this stored vacuum disappears almost instantly, I doubt I would even be able to hear any leak as the engine would be idling down as the leak occurred. There are no other symptoms or obvious vacuum leaks.

I'm no expert, so forgive me if I appear to oversimplify your issue... With that said, the engine's vacuum provides braking assistance through the brake booster. When the engine is off, there is no boost ergo no assistance and hard pedal. I think your brakes are functioning normally. Do you have any other symptoms..., hissing or something else that points to a vacuum leak?