hissing?

[ace2fine]

my pedal has started getting stiff at low speeds, mostly stop lights. once at the stoplight i hear a hissing from under the dash while holding the brake. i've always had the mushy gm pedal feel until a week or so ago. vacuum leak? what should i look for under there? also while its hissing, the pedal fades. rms fluctuate ( <- WTF? is that a word? doesn't look right) at the light. it was very cold out if that means anything.

[chevybrat]

vaccum leak/brake booster

[Mikz86TA]

X2 most likely

[ace2fine]

thats what i started thinking after reading about your brake issue. i hope not, its too cold out for all that!

[bespurcell]

X3

[ace2fine]

the haynes manual makes it sound easy as pie to replace a booster. will i need to bleed the brakes afterwards? i've never done a booster by the way.

on a side note, i did find some vac. lines near the booster. which ones affect the brakes and were the hell do they dive off to? at the fire wall the disappear into the fender and one even goes into a harness. WTF?

sorry all, but i never had to go past replacing the short lines at the caliper. so i'm in uncharted waters here. thanks in advance.

[bespurcell]

You will need to bleed the brakes.

[ace2fine]

thanks brandon, anything on the vac lines?

[bespurcell]

On mine there's a big vacuum line[about 3/4 O.D.] coming off the back of the intake manifold and going to the master cylinder.

[ace2fine]

yeah i got that too but i was reading a thread chevybrat started about her brakes. someone ha mentioned vac lines under the dash.? i've got some around the master cylinder/booster area. idk

[12sws27]

x4

[bespurcell]

I wouldn't worry about the other lines. Just follow the instructions in your Haynes manual.

[Jay-Sliver]

the vacuum line that darts off into your drivers fender is a line that feeds, or creates vacuum, in a vacuum pot that is inside the fender. This vacuum pot helps the little flapper doors in your HVAC system open and close when you change from foot to face or defrost etc..
thats just a little FYI. The only reason I know this is cus the nipple broke off my vacuum pot and I started to get very poor fuel milage. I tracked down the hissing sound and pinched the line off with Vicegrips. Problem Fixed!! only downfall to not having that vacuum pot there is the doors take a little longer to open and close..not a big deal.

As far as your problem goes, Booster for sure. As far as bleeding the brakes, you may be able to get away with NOT remoing the master cylinder from the booster. Im not 100&#37; sure on that. Best advice was already given, follow your haynes manual. They will usually lead you down the right path fairly clearly.

Jay