brake pedal vacume escape???

[BORDERBUM]

Ladies and Gentlemen,

Is it normal when you depress the brake pedal for a valve to open up and make a hissing noise under the dash?

I got under the dash and there is a valve of somesort , sorry for my lack of the correct parts names, when the brake pedal is depressed when engine is running there is a valve that lets air out, loud. When the brake is not depressed the valve is depressed by the brake pedal, when the brake is depressed the valve pops out and releases air.
I have yet to get my headlights to function correctly and it seems like not enough air is getting to them, could this be a reason? maybe a blockage somewhere and air has to escape here? I don't have a clue, my knowledge of vettes comes form what i have to fix on my 77 since my other two are far from being on the road. when i manually raise the lights the passenger side goes down when i shut the lights off, other than that nada.

git r done borderbum

 

[robert kirk]

When i got my 71 it had vac issues. the wiper door would go up when you cranked the motor. one headlight would go up the other would do a disco dance. i finally got a vac diagram and just traced all the lines out and made sure all the hoses went where they were supossed to go. ended up changing most all the vac accessorys, such as the switch you are talking about along with most of the headlight parts. vacc leaks can be a real problem on these old sharks. it was truely amazing how much vacc hose is on one of these old sharks. once you get it sealed up and everything working right its a pretty good system. low teck but effective. robert

 

[BORDERBUM]

the valve that i am talking about is under the dash and touches the brake pedal when it is NOT depressed. I took it out and cleaned it and it still releases the vacume, when the brake is depressed.

 

[Bob Chadwick]

Can you post a picture?

 

[BORDERBUM]

wish i could, but i dont have the d- camera. It actually touches the brake pedal and pops open like a writing pen(spring loaded). sorry i don't know any other way to explane it. there is a vacume hose connected to the back. and it is in a bracket under the steering collum.

 

[Bob Chadwick]

No idea. I don't see anything like it on my 77. I'm sure someone else will pop in with the answer.

 

[Stingray6974]

First, which car are you working on?
Second, does it have cruise control?

Mike

 

[JohnZ]

The area you're talking about (rear valve in the brake booster, under the dash) admits air into the back of the booster to power the diaphragm inside the booster which has engine vacuum on the front side of it; that's why there's a mesh air filter/sound reducing device right where the pedal pushrod enters the back of the booster. It's normal for air to rush into the booster there, but the felt and mesh filter should reduce the noise of the inrushing air so it's barely audible. If the felt/mesh filter has deteriorated and fallen out, then you'd hear the noise every time you step on the brake pedal.

 

[BORDERBUM]

im working on my 77 and yes it does have power steering, although it is not working, i did plug the vacume line for the power steering diaphram because it had a tear in it.

 

[JohnZ]

im working on my 77 and yes it does have power steering, although it is not working, i did plug the vacume line for the power steering diaphram because it had a tear in it.

Do you mean power steering or power brakes? There is no vacuum connection to the power steering.

 

[Stingray6974]

I think the train jumped tracks here. Do you mean cruise control and not power steering? Only two vacuum related sources contact the brake pedal. The power brake booster, as John mentioned, is attached to the pedal by a rod going forward. The other is the cruise control switch which mounts behind the pedal with a small plunger contacting the pedal arm. Plugging the line at the servo will not stop a vacuum leak. You will need to plug it at the transducer or the source.

Mike

 

[BORDERBUM]

i am sorry, me and my son are playing

i was asked if i had cruis control, yes i do have but it is not working do to those problems. sonce again sorry.

 

[BORDERBUM]

sorry mike, I have really messed up here today, I did plug it at the hose right before it enters the cruise control servo, I will plug it at the transducer and see if that is it. thank you for seeing through all the mess i had written. I will let you know what happens.


git r done borderbum

 

[Stingray6974]

Glad to help.

Mike