I went through and finished putting the new hardlines in my car and bled the brake system as i've researched. As i was pumping up the brake I could hear the brake booster vacuum line hissing (it is not hooked up, no motor in the car right now). It felt like i had literally no brake pressure, but I could see the fluid level fluctuating in the reservoir as I'd expect. Unfortunately I worked on it by myself tonight so I couldnt have someone spin the wheels and me apply the brake to see if they stopped. If I plugged the end of the vacuum line, the pedal pressure would rise to where it felt like a manual brake.....Anyways, would the brake booster technically be "recharging" on every stroke if the line is not hooked up, similar to how it would operate with engine vacuum?

Thanks,
AJ

EDIT: On second thought, i installed my volvo calipers upside down with the third bleeder screw on the bottom instead of the top. I'll be i have a huge air pocket in there somewhere.

wont be enough air in the booster to provide assistance for more than 5-6 pumps of the pedal. Any noise you hear after that is going to be a small amount of air pushed out of the other side of the booster as the diaphragm moves. No, it cant recharge itself without assistance from the engine.

If you have good vacuum and you plug the line into the booster with the car running and the pedal remains hard, you have issues and id suggest the booster has or is failing or you have something stuck somewhere.

The booster does nothing without the engine running. If the brakes don't bleed and work as normal (besides increased effort) there is something else wrong. Whether the booster is good, bad, or otherwise, the operation when not running is not affected.