Brake booster
Thread Starter
Instructor
Joined: Jul 2012
Posts: 174
Likes: 6
From: McDonough Georgia
Brake booster
Hey Guys,
I started noticing a vacuum sound every time I press on my brake peddle is this normal? I've learned to live with a spongy brake peddle, but I don't want to add to an already crummy braking system with a bad booster.
Thanks,
Al
I started noticing a vacuum sound every time I press on my brake peddle is this normal? I've learned to live with a spongy brake peddle, but I don't want to add to an already crummy braking system with a bad booster.
Thanks,
Al
Thread Starter
Instructor
Joined: Jul 2012
Posts: 174
Likes: 6
From: McDonough Georgia
I have been bleeding, and bleeding these brakes with no success. I upgraded the front calipers to Wilwood calipers mistakenly thinking that it would help and it didn't. The brakes will work but I am not able to lock the wheels when I stand on them.
Team Owner
Joined: Jul 1999
Posts: 65,492
Likes: 230
From: Orange Park Florida
I bought my '72 in '95 and in all them years early on, I have tried all sorts of solutions for that soft pillow we call brakes.....hit the pedal and it goes ehhhh, squisssssh to the firewall, and sharkey MAY feel like stopping.....I went to over bore sized truck m/cyl, took out that silly brake fail switch, commonly called a proportioning valve, which it is NOT and put in a simple splitter to the front brakes, and the line to the forward port on the m/cyl......rear brakes of course already had a T splitter so nothing done there.....
and still the brakes sucked, along with vacuum......
SO many years ago I picked up on the Hydroboost brake booster that runs off the power steering pump, installed it, and hit the brakes, sharkey stood on her nose and MY nose went into the wheel.....
takes a bit getting used to.....only 2-3 inches to lockup which is hard as a rock......not that soft feeling that goes to the firewall like a limp sister......
and still the brakes sucked, along with vacuum......
SO many years ago I picked up on the Hydroboost brake booster that runs off the power steering pump, installed it, and hit the brakes, sharkey stood on her nose and MY nose went into the wheel.....
takes a bit getting used to.....only 2-3 inches to lockup which is hard as a rock......not that soft feeling that goes to the firewall like a limp sister......
Tech Contributor
Joined: Jun 2004
Posts: 20,953
Likes: 962
From: I tend to be leery of any guy who doesn't own a chainsaw or a handgun.
I welcome any correction here, but it's my understanding that if you hear a hissing sound when applying the brakes, it's generally due to the disintegration of the foam filter/silencer at the brake pedal rod going into the booster.
Team Owner
Joined: Jul 1999
Posts: 65,492
Likes: 230
From: Orange Park Florida
Thread Starter
Instructor
Joined: Jul 2012
Posts: 174
Likes: 6
From: McDonough Georgia
I bought my '72 in '95 and in all them years early on, I have tried all sorts of solutions for that soft pillow we call brakes.....hit the pedal and it goes ehhhh, squisssssh to the firewall, and sharkey MAY feel like stopping.....I went to over bore sized truck m/cyl, took out that silly brake fail switch, commonly called a proportioning valve, which it is NOT and put in a simple splitter to the front brakes, and the line to the forward port on the m/cyl......rear brakes of course already had a T splitter so nothing done there.....
and still the brakes sucked, along with vacuum......
SO many years ago I picked up on the Hydroboost brake booster that runs off the power steering pump, installed it, and hit the brakes, sharkey stood on her nose and MY nose went into the wheel.....
takes a bit getting used to.....only 2-3 inches to lockup which is hard as a rock......not that soft feeling that goes to the firewall like a limp sister......
and still the brakes sucked, along with vacuum......
SO many years ago I picked up on the Hydroboost brake booster that runs off the power steering pump, installed it, and hit the brakes, sharkey stood on her nose and MY nose went into the wheel.....
takes a bit getting used to.....only 2-3 inches to lockup which is hard as a rock......not that soft feeling that goes to the firewall like a limp sister......
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
Corvette & Porsche 911: How Two Icons Conquered the Last 25 Years
Joe Kucinski
2027 Chevrolet Silverado 1500 First Look: Everything You NEED to Know!
Michael S. Palmer
5 Best & 5 Worst Corvette Daily Drivers
Joe Kucinski
The Headlights of Every Corvette Generation Explained
Joe Kucinski
5 Best & 5 Most Overrated Corvette Track Packages of All Time!
Joe Kucinski
Every 2027 Corvette Engine Explained
Joe Kucinski
Designer Imagines A Corvette That Looks More Like a Corvette Than the Corvette
Verdad Gallardo
10 Ugly Corvettes That We Still Kinda Love
Joe Kucinski
Top 10 Most Expensive Corvettes Ever Sold on Bring A Trailer
Brett Foote
Thread Starter
Instructor
Joined: Jul 2012
Posts: 174
Likes: 6
From: McDonough Georgia
Melting Slicks
Joined: Jun 2011
Posts: 3,123
Likes: 605
Test the brake booster. Connect a hand vacuum pump and see if it holds. Similar to this thread. ( I tested the unit outside of the car ) but you can do a similar test while on the car.
https://www.corvetteforum.com/forums...f-the-car.html
After this tests ok. Did you replace the pads when you where bleeding the brakes. If the pads have wear then it is very possible to trap air in the caliper pistons and the only way to remove this air is by pushing the piston in. I usually shim the pads to force them to completely push the pistons into the caliper. I also use my air compressor connected to the master cylinder and set to 10-15 PSI to pressurize the brake lines to bleed.
Thread Starter
Instructor
Joined: Jul 2012
Posts: 174
Likes: 6
From: McDonough Georgia
"live with spongy brake"
Test the brake booster. Connect a hand vacuum pump and see if it holds. Similar to this thread. ( I tested the unit outside of the car ) but you can do a similar test while on the car.
https://www.corvetteforum.com/forums...f-the-car.html
After this tests ok. Did you replace the pads when you where bleeding the brakes. If the pads have wear then it is very possible to trap air in the caliper pistons and the only way to remove this air is by pushing the piston in. I usually shim the pads to force them to completely push the pistons into the caliper. I also use my air compressor connected to the master cylinder and set to 10-15 PSI to pressurize the brake lines to bleed.
Test the brake booster. Connect a hand vacuum pump and see if it holds. Similar to this thread. ( I tested the unit outside of the car ) but you can do a similar test while on the car.
https://www.corvetteforum.com/forums...f-the-car.html
After this tests ok. Did you replace the pads when you where bleeding the brakes. If the pads have wear then it is very possible to trap air in the caliper pistons and the only way to remove this air is by pushing the piston in. I usually shim the pads to force them to completely push the pistons into the caliper. I also use my air compressor connected to the master cylinder and set to 10-15 PSI to pressurize the brake lines to bleed.
Had a 1976 L-82, 4-sp
Joined: Mar 2011
Posts: 5,338
Likes: 1,213
From: Some days your the dog and some days your the hydrant.
Royal Canadian Navy
I knew when my brake booster went bad. After I turned off the engine, I pulled the check valve from the front of the booster and didn't hear a hiss of rushing air into the booster. When I replaced the booster, I could pull the check valve a day after shutting down the car and would hear a hiss.
Last edited by resdoggie; Nov 24, 2016 at 09:06 AM.
Thread Starter
Instructor
Joined: Jul 2012
Posts: 174
Likes: 6
From: McDonough Georgia
I knew when my brake booster went bad. After I turned off the engine, I pulled the check valve from the front of the booster and didn't hear a hiss of rushing air into the booster. When I replaced the booster, I could pull the check valve a day after shutting down the car and would hear a hiss.
Team Owner
Joined: Jan 2006
Posts: 37,637
Likes: 3,118
From: Crossville TN
Bad booster. Seals are old/dried/shrunk and not sealing well.
Now, that will improve the power-assist function of the brakes...but it will NOT tighten-up the brake pedal problem. That is due to air in the system or very old brake fluid which as ingested some water into it over the years. Also, if you have any OLD rubber brake hoses on ANY of your calipers, you NEED to replace them. The rubber on the inside of those hoses deteriorates and tends to block off fluid flow. They can cause continuous partial apply of that brake set [and constantly build heat!] or cause spongy feel in the pedal because they tend to 'bulge' under pressure.
Now, that will improve the power-assist function of the brakes...but it will NOT tighten-up the brake pedal problem. That is due to air in the system or very old brake fluid which as ingested some water into it over the years. Also, if you have any OLD rubber brake hoses on ANY of your calipers, you NEED to replace them. The rubber on the inside of those hoses deteriorates and tends to block off fluid flow. They can cause continuous partial apply of that brake set [and constantly build heat!] or cause spongy feel in the pedal because they tend to 'bulge' under pressure.
Last edited by 7T1vette; Nov 24, 2016 at 11:23 AM.
Thread Starter
Instructor
Joined: Jul 2012
Posts: 174
Likes: 6
From: McDonough Georgia
Bad booster. Seals are old/dried/shrunk and not sealing well.
Now, that will improve the power-assist function of the brakes...but it will NOT tighten-up the brake pedal problem. That is due to air in the system or very old brake fluid which as ingested some water into it over the years. Also, if you have any OLD rubber brake hoses on ANY of your calipers, you NEED to replace them. The rubber on the inside of those hoses deteriorates and tends to block off fluid flow. They can cause continuous partial apply of that brake set [and constantly build heat!] or cause spongy feel in the pedal because they tend to 'bulge' under pressure.
Now, that will improve the power-assist function of the brakes...but it will NOT tighten-up the brake pedal problem. That is due to air in the system or very old brake fluid which as ingested some water into it over the years. Also, if you have any OLD rubber brake hoses on ANY of your calipers, you NEED to replace them. The rubber on the inside of those hoses deteriorates and tends to block off fluid flow. They can cause continuous partial apply of that brake set [and constantly build heat!] or cause spongy feel in the pedal because they tend to 'bulge' under pressure.
I'll followup with an updated post as I continue to swap out parts.
Last edited by ONeill202; Nov 24, 2016 at 12:11 PM.
Team Owner
Joined: Jul 1999
Posts: 65,492
Likes: 230
From: Orange Park Florida
I knew when my brake booster went bad. After I turned off the engine, I pulled the check valve from the front of the booster and didn't hear a hiss of rushing air into the booster. When I replaced the booster, I could pull the check valve a day after shutting down the car and would hear a hiss.
Get some advice from a junkyard as to what vehicles a HydroBoost comes off of......or if it's a U pullit yard....bring your tool set and start lookin'.....
Le Mans Master
Joined: Dec 2007
Posts: 6,422
Likes: 591
From: McHenry Illinois
Years ago, my brake pedal was spongy, I bled it till there was no air, I eventually determined the reaction disc in the booster was soft and causing it. Instead of replacing the booster, which would have fixed it, I changed over to the hydro boost without opening a brake line, I instantly had a good hard pedal. I don't see ever needing better brakes than what it has now, I can lock them up anytime I want.
Had a 1976 L-82, 4-sp
Joined: Mar 2011
Posts: 5,338
Likes: 1,213
From: Some days your the dog and some days your the hydrant.
Royal Canadian Navy
My '72 passed that test several times, just says the booster is good, basically......not that it's good enough.....
Get some advice from a junkyard as to what vehicles a HydroBoost comes off of......or if it's a U pullit yard....bring your tool set and start lookin'.....
Get some advice from a junkyard as to what vehicles a HydroBoost comes off of......or if it's a U pullit yard....bring your tool set and start lookin'.....
Team Owner
Joined: Jul 1999
Posts: 65,492
Likes: 230
From: Orange Park Florida
Correct and I also agree with 7T1vette. But if you have a bad booster with the symptons I described, there's a good chance you have a vacuum leak also i.e. booster can't maintain a vacuum. So when you hit the brakes hard at speed, your idle drops and maybe your vacuum. Not good. As for hydroboost, it's an option that's just as effective as a properly functioning oem brake system. That's why I haven't converted - no need.
believe me, you will be FAR happier for the conversion....
