Require advice diagnosing brake issues

[david.]

Hello everybody! I was investigating a braking issue with my mrs' Hyundai Elantra 2003. I would usually have to pretty much stand on the brakes to make the car stop. The system's been bled and I noticed a crust of rust on the edge of the rotor surface so got that machined down. It seemed to help a tiny bit. Well as I was playing around with it before I noticed that if the brake pedal is pushed down fast (while the car is on) it made a hissing sound, very similar to an air leak or something. I followed the sound and found out it came from this:

It seems like that's the part which pushes into the brake booster/master cylinder assembly located behind the glove box. Would this be a sign that I need the brake booster replaced? Or is it nothing and I've hit a brick wall in my attempt to source the problem?

Any help would be greatly appreciated guys :)

[Hiro]

You say you have to stand on the brakes to make the car stop, but how is the actual pedal feel? Does it feel like you're stepping on a brick, or does it still feel normal just the car doesn't respond.

A slight "hissing" noise is perfectly fine when you repeatedly pump the brakes, this is the air going IN to the brake booster (it is a vacuum booster remember, so normally it is a vacuum). If you turn the car off and pump the brake pedal you should hear the hiss as the pedal progressively gets firmer and firmer (this is the vacuum booster effect being depleted).

[david.]

With the vehicle turned on at a stop I can easily push the brake all the way down, but while moving it feels like I'm pushing down onto a brick. And fair enough that makes sense. Not sure what the cause is here then.. I don't see any signs of fluid leak either.