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Hissing brake pedal?
Thread Starter
Pro
Joined: Mar 2006
Posts: 700
Likes: 2
From: Spring Hill Florida
Hissing brake pedal?
Yesterday driving home I pulled up to a stop light and there was a hissing sound (air escaping) coming from the brake pedal. Obviously there is a leak in the power brake system, somewhere. Before I get into it; has anyone had this experience?
Race Director
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Thread Starter
Pro
Joined: Mar 2006
Posts: 700
Likes: 2
From: Spring Hill Florida
Checked under the hood all around the booster, no hissing. Can only hear the air escaping while in the car. Went under the dash and pressed on the brake and the sound is coming from under the dash? If I hold down the pedal the engine will want to stall. So vacuum is leaking from somewhere.
Le Mans Master
Joined: Aug 2007
Posts: 8,735
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From: WV
Checked under the hood all around the booster, no hissing. Can only hear the air escaping while in the car. Went under the dash and pressed on the brake and the sound is coming from under the dash? If I hold down the pedal the engine will want to stall. So vacuum is leaking from somewhere.
Racer
Joined: Jul 2012
Posts: 262
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From: South Lyon, MI
It definitely sounds like the brake booster. I had one in my S10 give similar symptoms. The booster might seal up when not bothered, but once you push the brakes the diaphragm could be losing it's seal internally.
Thread Starter
Pro
Joined: Mar 2006
Posts: 700
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From: Spring Hill Florida
It has always gone down a little when starting. The brakes work fine except when it's hissing and then it seems to revert to "hard" brakes-no booster. I'm sure it's a bad seal or something in the rear. I found one on line for $112.00. Not to sure how to replace it.
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Race Director
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youtube is your friend. It is suppost to go down a little. Four nuts and a clip.
Last edited by antfarmer2; Jun 17, 2015 at 08:44 AM.
Safety Car
Joined: Aug 2009
Posts: 3,752
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From: Melbourne, Victoria, Australia
Did not affect braking assistance much at first, turned out the diaphragm in the booster had torn.
You can get them repaired however most will not want to try, the plastic has hardened with heat over the years and can break when they try to open it.
I got a new one and make sure i do not bleed the brakes the old fashioned way, that extra travel usually does the diaphragm in my experience.
Is a fairly simple straight forward job to replace the booster.
Racer
Joined: Oct 2012
Posts: 265
Likes: 5
From: Phoenix AZ
You are in for a treat. You're gonna need lots of extensions for your ratchet. 1/4 inch will be easiest. There just isn't much room under the dash to work. Remove the drivers seat. I would tape either a towel or sheet of plastic to the firewall under the dash so when you drop the nuts, and you will, they won't disappear into the black hole the resides under the steering column. You're gonna be lying on your back trying to hold a flashlight in your teeth while trying to get your socket on the bolt with one hand and working the ratchet with the other. Plan on cussing a lot. Beer is your friend. Before you put yourself through this ordeal, and yes that is what this is, check the check valve on the booster. If it's bad you could save yourself a lot of time, money, and aggravation.
Thread Starter
Pro
Joined: Mar 2006
Posts: 700
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From: Spring Hill Florida
I watched a video on YouTube and I think I will ask my Corvette garage what they will charge. They get $75/hr. Maybe 3 hours? Might be worth it. I'm 6'2" 250 lbs. Could be a squeeze?
Race Director
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use some tape in the socket to hold the nut
Last edited by antfarmer2; Jun 18, 2015 at 08:34 AM.
Safety Car
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Have you checked the vacuum operated cruise disengage switch for leaks? It is mounted by the brake light switch, behind the brake pedal, under the hush panel. Remove the panel, start the car, press the brake pedal with your hand and listen. The switch is only activated when you depress the brake pedal. They are plastic and do go bad. It's a fast an easy check before tearing out your booster.
If it leaks, you can hear a hiss when you press the pedal.
If it leaks, you can hear a hiss when you press the pedal.
Race Director
Joined: Jan 2012
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From: United States
Have you checked the vacuum operated cruise disengage switch for leaks? It is mounted by the brake light switch, behind the brake pedal, under the hush panel. Remove the panel, start the car, press the brake pedal with your hand and listen. The switch is only activated when you depress the brake pedal. They are plastic and do go bad. It's a fast an easy check before tearing out your booster.
If it leaks, you can hear a hiss when you press the pedal.
If it leaks, you can hear a hiss when you press the pedal.
Racer
Joined: Oct 2012
Posts: 265
Likes: 5
From: Phoenix AZ
Don't give up so fast. If a mechanic can do it, you can. No special skills required. You'll actually be pretty comfortable down there. And the convertible makes it easier to get in and out. The hardest part will be finding a combination of extensions that will work. Cover the studs the seat attaches to with a towel so they don't dig in. A helper would be nice for when you drop something. And lots of beer. And music. You'll be fine.
