Air Leak from brake piston until pedal is depressed. Concern

[CanuckQx4]

EDIT: Video I made

http://img64.imageshack.us/i/p1010264.mp4/




So I just noticed a weird noise coming from my brake pedal, it sounds like an air leak, you can hear it over the engine inside the cabin. I got my head down in my driver footwell with the car running and could hear a constant air leak. Poked around and found it was coming from the piston/arm of the brake pedal assembly. Right where it transfers through the firewall.

There was a little rubber accordian looking boot and if i touched that with my fingers I could disrupt the airflow and stop it in some places briefly

Then I noticed if I depressed the brake pedal, the noise would go away instantly as soon as the pedal was depressed.

I also noticed if I listenned to it leaking, a constant audible air leak, and then turned off the engine and kept listenning to the noise and it slowly died down after about 5 seconds, like it ran out of air pressure to leak...

What could be leaking and should I drive the vehicle??

Im gonna scour the FSM for info and a blowup

[CanuckQx4]

I couldnt see on the engine side of the firewall as its 10pm and I have no good source of lighy. But Im assuming there may be an vacum hose or line running to that point? Or something is just internally leaking passed a blown seal or soemthing

[ARKQX33V6]

Vacuum booster provides a negative pressure to the main actuator and then removes this pressure as you use it. If you're leaking the engine would run badly. Feel around the square with 4 bolts for leaks and listen there as some one pushes the peddle. Also start up car use brakes all off brakes then shut car off, push on brakes and start car. Does the peddle fall away do not pump the brakes. Describe the action

[CanuckQx4]

The car kind of does run badly....

The square with 4 bolts right on the firewall is where its coming out, thats where this is a rubber looking boost coverring the innards of whatever goes through the firewall, and if I touch/move the boot with my finger, the airflow noise gets disrupted.

Its not coming out with ALOT of force, but its enough pressure to be audible...

Im a little confused with that brake test you posted though

[Chuck Tribolet]

Is there air coming out, or going in? I suspect you have a leak in the brake booster. I suspect air going in.

[CanuckQx4]

I couldnt really feel the air it wasnt that strong. Im sure i can figure it out with a match and a smoke in a minute though.

[Chuck Tribolet]

One thing to keep in the back of your head: if it's the booster, and the leak suddenly gets worse on the road, you are going to need
a lot of force on the brake pedal. Think both feet. Maybe even see if you can get both feet on ahead of time.

Related story. When I was in college, and dinosaurs roamed the earth, my roommate's GF (later his wife) had her folks Mercedes out one
night. When she came home, she decided to not wake up, and shut the ignition off to coast in. No power brake, she hit the back wall
of the garage. (And, no she wasn't trying to sneak. She was over 21, and her parents were cool about her BF.

[CanuckQx4]

Ya my qx4 has stalled out on me before while driving and I realized how hard it was to use the brakes without power lol

How big of a fix could this be?? Does it sound like I need a new pedal assembly or something??

Im going to go make a video, I was hoping ARK would jump back in with why he thought that test would help.

Sucks

[CanuckQx4]

quick video I made before I ran out of sun when I got off work. The noise/leak wasnt audible when gently pushing the pedal like it was yesterday... took some force. I hope the video came out ok and someone can get an idea what Im talking about from it. Hope the audio came out good.

http://img64.imageshack.us/i/p1010264.mp4/

[CanuckQx4]

got the video working!!

[CanuckQx4]

[VG33QX4]

its normal to hear air sound when depressing the brake

if you feel a lack of pedal force then probably the booster has a blown seal. usually you would be able to hear the engine rev up high during this process due to vacumn leak

[CanuckQx4]

Ya thats what its doing now its only leaking when i despress the pedal

But when I first made this post there was air coming out of the red part I circled with no brake pedal pressure, would that still be the brake booster?? (I thought that was mounted to my firewall)

If the part suspected isnt expensive or hard to replace, I'd love to just change it.

I think my brake pedal isnt stiff enough and doesnt stiffen up really if you pump it a bunch of times.

I dont really have a car to compare the feel to though.

I think the air might have only been leaking out the other day without pedal pressure because it was the warmest day of the week I blieve and maybe something warmed up enough to expand... I dunno

But I dont want to die cause of a brake failure lol

[VG33QX4]

Temp should have no bearing if it feels the same with the car running or car off you need a booster. If pumping the pedal changes the force by which is applied to the brake pads then you have a failed master cly. Otherwise you will and probably most likely need a replacement brake booster they run about 100-150

[CanuckQx4]

Could you possibly give me a way to easily diagnose which I would need??

Im in a maintenance fever this week (just fixed 3 sensors and loctited my power valves this morning)

Tomrrow Im doing all my control arm bushing in polyurethane (already removed all4 just need to be brought to the shop)

Then if I can get this brake problem figured out, fix whatever is broken next weekend and maybe by then my stainless brake lines will have came in and my fuel filter and I'll be up to date and get some relaxing miles out of this car lol

Would love to feel safe on the brake diagnosis though

Thanks so far!!