Need help with brakes - Please!
Thread Starter
Safety Car
Joined: Oct 1999
Posts: 4,679
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From: Honolulu HI
Need help with brakes - Please!
I parked the Vette Sunday and everything was okay. I got it out tonight and as soon as I started to move it I realized I had no power brakes. I can hardly push the brake pedal down. It is like when you stall the engine and can harldy push the pedal but it is that way all the time. This happened while it was sitting not while I was driving. Has to be something in the power brake system. Any help much appreciated, I hate working on brake systems! Yuk! :eek:
Aloha,
Larry
Aloha,
Larry
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Joined: Oct 2000
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From: Enter Post Count Here
Re: Need help with brakes - Please! (Larry Mackey)
Sounds like your brake booster(Big black round piece between the master cylinder and firewall) split. Fortunately its not too hard, nor expensive to replace. Its about $80 from Autozone, with a lifetime warrantee, or around $250 from GM.
To replace it, you simplye need to remove the drivers seat, wedge yourself in there, unbolt it, climb out, unbolt it from the master cylinder, bolt the new one in place(not permanently, you need to make adjustments later), then rebolt it to the brake pedal and firewall. Now, climb in, press on the pedal, decide if pressure is too hard or soft. If its too hard, screw the bolt in on the booster, if its too soft, unscrew it. You'll have to hold the base with a pair of pliers or something, because it will spin. Rebolt it to the master cylinder, test pressure, repeat as necessary. Bolt booster to master cylinder permanently(not too tight), and drive away. :) Total time the first time, about 2 hours.
Before you decide to replace it, make sure none of the vacuum lines on the plenum have come loose.
Good luck.
[Modified by NoWorries, 1:05 PM 2/28/2002]
To replace it, you simplye need to remove the drivers seat, wedge yourself in there, unbolt it, climb out, unbolt it from the master cylinder, bolt the new one in place(not permanently, you need to make adjustments later), then rebolt it to the brake pedal and firewall. Now, climb in, press on the pedal, decide if pressure is too hard or soft. If its too hard, screw the bolt in on the booster, if its too soft, unscrew it. You'll have to hold the base with a pair of pliers or something, because it will spin. Rebolt it to the master cylinder, test pressure, repeat as necessary. Bolt booster to master cylinder permanently(not too tight), and drive away. :) Total time the first time, about 2 hours.
Before you decide to replace it, make sure none of the vacuum lines on the plenum have come loose.
Good luck.
[Modified by NoWorries, 1:05 PM 2/28/2002]
Thread Starter
Safety Car
Joined: Oct 1999
Posts: 4,679
Likes: 2
From: Honolulu HI
Re: Need help with brakes - Please! (NoWorries)
No Worries,
Would a broken vacuum line cause the brakes to be that bad? Actually I had alraady thought of that because the idle also seems to be "up & down" somewhat. It was just too late tonight to start checking all twelve miles of vacuum lines. Is the big vacuum line between the brake booster and the plenum the only one that would affect the brakes? Thanks again.
Aloha,
Larry
Would a broken vacuum line cause the brakes to be that bad? Actually I had alraady thought of that because the idle also seems to be "up & down" somewhat. It was just too late tonight to start checking all twelve miles of vacuum lines. Is the big vacuum line between the brake booster and the plenum the only one that would affect the brakes? Thanks again.
Aloha,
Larry
Race Director
Joined: Oct 2000
Posts: 16,477
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From: Enter Post Count Here
Re: Need help with brakes - Please! (Larry Mackey)
Hey Larry,
The smaller lines shouldn't make *that* much of a difference, the one's that run the cruise control, fuel pressure, and EGR shouldn't be enough of a vacuum loss to cause the whole system to die.
On the other hand, the vacuum booster line(left rear of plenum) is huge, and would certainly cause the car to run bad and the booster to not work. Has the plenum been off the car recently? There is a sensor in the bottom that if it wasn't tightened, and fell out, its a tremendously big hole. If it hasn't been out recently though, thats probably not the cause. Next are two lines on the throttle body, one is for the Positive Manifold pressure, and I'm not sure what the other is, but either of these could be a problem.
If those four are in good shape, its most likely a ripped diaphram in the booster itself, or a cracked case.
A ripped diaphram would most likely cause a deteriorated idle, although I don't remember if it did when mine went. In the eyes of the engine, its still a vacuum leak, even though its a long ways from the engine.
Good luck,
Canyon
The smaller lines shouldn't make *that* much of a difference, the one's that run the cruise control, fuel pressure, and EGR shouldn't be enough of a vacuum loss to cause the whole system to die.
On the other hand, the vacuum booster line(left rear of plenum) is huge, and would certainly cause the car to run bad and the booster to not work. Has the plenum been off the car recently? There is a sensor in the bottom that if it wasn't tightened, and fell out, its a tremendously big hole. If it hasn't been out recently though, thats probably not the cause. Next are two lines on the throttle body, one is for the Positive Manifold pressure, and I'm not sure what the other is, but either of these could be a problem.
If those four are in good shape, its most likely a ripped diaphram in the booster itself, or a cracked case.
A ripped diaphram would most likely cause a deteriorated idle, although I don't remember if it did when mine went. In the eyes of the engine, its still a vacuum leak, even though its a long ways from the engine.
Good luck,
Canyon
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Joined: Aug 2001
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From: Waco Tx
Re: Need help with brakes - Please! (Larry Mackey)
Same exact thing happened to the 90 vette I used to have. Drove to work in the morning and everything was fine, went to drive home from work and was surprised to find I had no brakes. It felt like trying to kick a door down to get the car to stop. It turned out to be a crack in the power booster. Not to hard to change or very expensive, just hard to cram yourself under the dash to change it. Good luck. :)
Pro
Joined: Aug 1999
Posts: 517
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From: Fort Myers FL
Re: Need help with brakes - Please! (Larry Mackey)
Same thing happened to me this week. The car has been idleing roughly for two weeks...an on and off thing. Then this week I had to sudenly use both feet to depress the brake peddle...then it would work fine a few times, then bad again. I also think it is my brake booster.
Steve
Steve
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From: Out Where the Buses Don't Run, Eglin AFB/ Niceville FL
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Re: Need help with brakes - Please! (Larry Mackey)
My 89 did the same thing a while back. It was the booster. Covered under warranty so I didn't get to play with it.
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Burning Brakes
Joined: Feb 2001
Posts: 841
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From: Wichita, Ks, USA
Re: Need help with brakes - Please! (89ragtop)
I Had the same thing happen where you have to press very hard to stop the car. On mine I also heard a vacum type leak from inside the car. Kindof a WAHH" type hiss. I had the booster replaced. Problem solved. Not real cheap though.
