Do I have a brake problem?
Thread Starter
Instructor
Joined: Jun 2004
Posts: 182
Likes: 0
From: Sun Peaks British Columbia
Do I have a brake problem?
I need some comments here. I replaced the brake rotors, calipers, pads, proportioning valve, master cylinder, brake lines and fluid on my 79', (in short, everything). I then had a shop power bleed the system.
The brake pedal still travels about two inches before it feels solid. Is this normal. I've been told that bleeding the system is difficult on the C-3s. The car seems to brake OK.
What do you think?
The brake pedal still travels about two inches before it feels solid. Is this normal. I've been told that bleeding the system is difficult on the C-3s. The car seems to brake OK.
What do you think?
Tech Contributor
Joined: Aug 1999
Posts: 15,175
Likes: 3,987
From: Connecticut, USA
Vette brakes are not hard to fix but you must understand the system.
First did you bench bleed the M/C? Sounds like you still have air in the system.
Next you have to be sure the rotor runout is under .005" under.003" is better. Do a search here because there has been 5 years of brake questions here-all covering your problems. If you don't get anywhere let me know and I'll spend more time with you on it.
Gary
First did you bench bleed the M/C? Sounds like you still have air in the system.
Next you have to be sure the rotor runout is under .005" under.003" is better. Do a search here because there has been 5 years of brake questions here-all covering your problems. If you don't get anywhere let me know and I'll spend more time with you on it.
Gary
Melting Slicks
Joined: Jan 2000
Posts: 2,386
Likes: 3
From: far, far away
Originally Posted by yellovette
The brake pedal still travels about two inches before it feels solid. Is this normal.
But I do recall that there is a sequence.... The only major thing you've got going that I didn't have is a new master. That makes me suspect air still in it. Good luck!
Le Mans Master
Joined: Sep 2000
Posts: 5,635
Likes: 4
From: Orlando Floriduh
Maybe the shop didn't realize that the rear calipers have two bleeder screws and the halve are not interconnected like the front. Omitting the extra bleeders will cause the system to always feel spongey.
Race Director
Joined: Mar 2001
Posts: 11,601
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From: San Francisco CA
St. Jude Donor '07
I think procedure for bleeding is shortest to longest for vettes, I forget why.
Also, they don't go out very often, but the booster may be bad. I know a lot of people here will tell you otherwise, but mine wouldn't stop even though I replaced everything else. Once I replaced the booster, it locks up all four.
Also, they don't go out very often, but the booster may be bad. I know a lot of people here will tell you otherwise, but mine wouldn't stop even though I replaced everything else. Once I replaced the booster, it locks up all four.
Thread Starter
Instructor
Joined: Jun 2004
Posts: 182
Likes: 0
From: Sun Peaks British Columbia
OK thanks for those replies. I'll try and cover some of your points;
1) As far as runout on the rotors, I put new rotors on, so that should not be a problem.
2) I did bench bleed the new master cylinder. I think I got all the air out of that.
3) As far as the bleed process goes, the shop that did it, is a Vette shop. Figured they would know about all the bleed points and have done it right.
4) The brake booster was not changed. It's definitely working to power the brakes. Could it still be worn enough to cause excessive pedal travel???????
1) As far as runout on the rotors, I put new rotors on, so that should not be a problem.
2) I did bench bleed the new master cylinder. I think I got all the air out of that.
3) As far as the bleed process goes, the shop that did it, is a Vette shop. Figured they would know about all the bleed points and have done it right.
4) The brake booster was not changed. It's definitely working to power the brakes. Could it still be worn enough to cause excessive pedal travel???????
Racer
Joined: Jan 2004
Posts: 263
Likes: 1
From: 20,000 leagues under the sea
Originally Posted by yellovette
4) The brake booster was not changed. It's definitely working to power the brakes. Could it still be worn enough to cause excessive pedal travel???????
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Thread Starter
Instructor
Joined: Jun 2004
Posts: 182
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From: Sun Peaks British Columbia
Originally Posted by 68raggtop
One thing to consider... the master for power brakes and manual are not the same. Is it possible you were given a manual master cylinder? If my memory is right, the hole in the piston for the pushrod is much deeper on the manual brake masters.
Race Director
Joined: Mar 2001
Posts: 11,601
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From: San Francisco CA
St. Jude Donor '07
Originally Posted by yellovette
4) The brake booster was not changed. It's definitely working to power the brakes. Could it still be worn enough to cause excessive pedal travel???????
Before I replaced mine, I would press and nothing would happen. It's not supposed to happen, but even when I bottomed out the pedal, the car would hardly stop. There's supposed to be a mechanical backup so that if the vacuum fails, you should be able to still stand on the brakes and stop the car. On a >25 year old car, it's certainly something to consider if all else fails. You don't even have to crack the brake lines, just have to crawl under the dash.
As far as bore size on your mc, I don't think there's a way to check without at least moving it away from the booster, I don't think you need to crack the lines. I'll try to find something on how to tell which one is which.
Melting Slicks
Joined: Feb 2000
Posts: 3,052
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From: Vancouver BC, Canada
Originally Posted by yellovette
OK thanks for those replies. I'll try and cover some of your points;
1) As far as runout on the rotors, I put new rotors on, so that should not be a problem.
1) As far as runout on the rotors, I put new rotors on, so that should not be a problem.
Team Owner
Joined: Mar 2002
Posts: 24,160
Likes: 78
Originally Posted by Buffalo Dude
Before I replaced mine, I would press and nothing would happen. It's not supposed to happen, but even when I bottomed out the pedal, the car would hardly stop. There's supposed to be a mechanical backup so that if the vacuum fails, you should be able to still stand on the brakes and stop the car. On a >25 year old car, it's certainly something to consider if all else fails. You don't even have to crack the brake lines, just have to crawl under the dash.
Anyhow an easy test for a booster is to just pump up the brakes with the engine off, then hold the pedal down while you crank up the engine. If the pedal drops once she's running, then your booster is fine.
Race Director
Joined: Jan 2004
Posts: 18,191
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From: Snake handler
Originally Posted by yellovette
Wow! Could be I got a non-power brake master cylinder. Don't know how I'd be able to tell now.
Hope that helps.
pm
Thread Starter
Instructor
Joined: Jun 2004
Posts: 182
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From: Sun Peaks British Columbia
Thanks PM, I'll definitely have a look at that. Also I'll probably try BD's suggestion, ( which I've seen discussed on other threads) to put on a new brake booster. I know it doesn't make a lot of sense but several others have experienced the same problems as me and corrected same by changing the booster. I've never taken one apart but I'm thinking that maybe there's more space than we think between the booster rod and the brake pedal rod.
yellovette
yellovette