Brake pedal can be pushed nearly completely down to the floor when standing

[[__--MUD--__]]

"steering wheel is turned to the end stop" isn't a hissing noise... That coming from the pump. If your just talking about the hiss when you hit the pedal- thats normal.

[ffl]

if the infos in the link i posted are correct, then why does a correct working hydro boost brake produce hissing noises when pushing the pedal harder than in a normal braking situation and produce no noises when braking not that hard? and they are talking about the level of pressure on the pedal and not how fast you are hitting it, i think.

by the way, i also think that the noise is coming from the pump, but i don't know if it's normal. could be that the pressure in the system is rising during hard braking...

[Yetti]

see this all the time.
First off even if the engine was off the hydro boosts accumulator hold about 5 pedal pumps worth of effort.
I believe what you guys are seeing is the bad master cylinder. if you apply the brakes very slowly its like you can step past the pedal effort of normal brakes?
when you step on them or jab them as you apply they work normal?

I suspect the seals and bore are wearing. I see it more on Burbs but its the same. the bore wears where the most action is. the problem with that is the seals wear also. when the seal lip is worn to where it can't expand and follow the shape of the bore it lets fluid slip by. that's what your seeing. when you jab the brakes you expand the seals enough to catch fluid and work normal.

replace the Master cylinder and things should be normal again.

[ffl]

perhaps it could be like that. when the car is not moving it's possible to slowly push the pedal all the way down when applying enough force.
it's way more force that is necessary to hold the car in place.

when driving, the brakes work like they should and there's no problem.

is it really necessary to already change the cylinder or can i leave it like that at the moment? i mean normal braking is no problem even when braking very slowly, also hard braking when driving is no problem.

by the way, how long does the hydro boosts accumulator hold the pressure to get brake assist when the engine is not running? is it only for an short time, say 10 minutes or does it last for a much longer time, several weeks or so?

[s_c5519]

Originally Posted by Yetti

see this all the time.
First off even if the engine was off the hydro boosts accumulator hold about 5 pedal pumps worth of effort.
I believe what you guys are seeing is the bad master cylinder. if you apply the brakes very slowly its like you can step past the pedal effort of normal brakes?
when you step on them or jab them as you apply they work normal?

I suspect the seals and bore are wearing. I see it more on Burbs but its the same. the bore wears where the most action is. the problem with that is the seals wear also. when the seal lip is worn to where it can't expand and follow the shape of the bore it lets fluid slip by. that's what your seeing. when you jab the brakes you expand the seals enough to catch fluid and work normal.

replace the Master cylinder and things should be normal again.

Well in my case, I currently have two 08's and both do the same thing. I have had another 08 before and a brand new 09 from the factory do the exact same thing too. I am hoping I did not get 5 bad copies in a row. lol...

So I don't want to panic anyone into thinking somethings wrong. I am guessing all 08-09's have that sound. In the case of his '05 though, I have no clue...