brake issue... Master cylinder????
Thread Starter
Instructor
Joined: Mar 2006
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brake issue... Master cylinder????
I live in MI and I took my 1982 vette out of storage a few days ago, and the brakes are supper spongy, you couldnt stop fast if you wanted to. So I checked it out and the master cylinder seems to be leaking a little bit. I checked all the brake lines and brakes everything looks good. I also pulled the brake lines off of the mastercylinder and screwed in some plugs, pumped the breaks and they were still spongy. So I'm pretty sure that my master cylinder just isn't producing the pressure it should be. Any one know if there is a good rebuild kit out there or if I should just get a new one, and if so from where???? Thanks in advance guys.
Instructor
Joined: May 2003
Posts: 128
Likes: 1
From: Lake Geneva WI
Leaking from where? You removed the lines from the MC and plugged the openings and stepped on the brake pedal and it felt spongy?
I would start with replacing the MC and get someone to help you and bleed the entire system. Be patient especially at the back wheels as the fluid has a long way to go to get there. Removing the lines introduced air to the system. Make sure you follow the sequence of order as to which wheels to do in what order.
Mike
I would start with replacing the MC and get someone to help you and bleed the entire system. Be patient especially at the back wheels as the fluid has a long way to go to get there. Removing the lines introduced air to the system. Make sure you follow the sequence of order as to which wheels to do in what order.
Mike
C6 the C5 of tomorrow
Joined: Nov 2000
Posts: 6,665
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From: Twin Cities Minnesota
I would start by testing the MC by pumping it up and applying pressure and holding it for like a minute. (engine running if you have power brakes)
You want 50 to 75 lbs on the pedal. If it holds everything is good, if it drops you have a leak, if it's spongy you have air.
Since you pluged the MC and have a spongy pedal you know you have air in it. You have to bleed the MC.
You want 50 to 75 lbs on the pedal. If it holds everything is good, if it drops you have a leak, if it's spongy you have air.
Since you pluged the MC and have a spongy pedal you know you have air in it. You have to bleed the MC.
Team Owner
Joined: Mar 2002
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Where did you see a leak? At the line fittings?
Plugging up the MC isn't really a good test because you'll introduce air into it in the process. But using this method, can you get the pedal to sink to the floor if you hold a steady pressure on it? If so, that means the piston seals are gone and the fluid is internally bypassing. This is typically how the MCs die.
Plugging up the MC isn't really a good test because you'll introduce air into it in the process. But using this method, can you get the pedal to sink to the floor if you hold a steady pressure on it? If so, that means the piston seals are gone and the fluid is internally bypassing. This is typically how the MCs die.
Team Owner
Joined: Sep 2006
Posts: 31,278
Likes: 4,372
From: Westminster Maryland
Hi HH303,
If the bore in the master cylinder isn't pitted from rust or scored, it can be rebuilt with a seal/piston kit. If the master cylinder needs to be sleeved it's usually less expensive to buy a new one.
Regards,
Alan
If the bore in the master cylinder isn't pitted from rust or scored, it can be rebuilt with a seal/piston kit. If the master cylinder needs to be sleeved it's usually less expensive to buy a new one.
Regards,
Alan
Thread Starter
Instructor
Joined: Mar 2006
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The MC shouldnt have had air in it. Car has 50,000 miles and all original (other than some fresh paint) Brakes were never messed with and there aren't any leaks in the line. Im not sure where it was leaking from the MC I could just see some fluid dripping out of it, it was kind of hard to tell. But from the sounds of it I should take it right off and take a good look at it to see what I've got. I think it has to be in there because like I said everything eles looks great no leaks, rust, holes... Thanks guys. By chance does any one know where to get a good new one if thats what I end up having to do?? Car does have power brakes too by the way.
Racer
Joined: Aug 2008
Posts: 413
Likes: 22
From: Justin TX
I would suggest purchasing a hand pump vaccum bleeder, yoou will have to have one to replace the MC anyway. The old pump up and bleed does not work on a C3 vette. I replaced all the lines on my 69 and could never get the brakes to pump up or get fluid to the calipers. I was certain the Mc had failed but checked with another C3 buddy and went and got the bleeder. Start at the right rear outside, (pump till full clear fluid for a while, you will get lots of foam) then move to inside, then to the left same proceedure, then right front, then left front. My hand was sore for weeks after this proceedure. I would try this before replacing the MC, especially since the lines were separated and plugged.
Team Owner
Joined: Mar 2002
Posts: 24,160
Likes: 78
The MC shouldnt have had air in it. Car has 50,000 miles and all original (other than some fresh paint) Brakes were never messed with and there aren't any leaks in the line. Im not sure where it was leaking from the MC I could just see some fluid dripping out of it, it was kind of hard to tell. But from the sounds of it I should take it right off and take a good look at it to see what I've got. I think it has to be in there because like I said everything eles looks great no leaks, rust, holes... Thanks guys. By chance does any one know where to get a good new one if thats what I end up having to do?? Car does have power brakes too by the way.
You could rebuild it, but honestly MCs are so cheap I wouldn't bother. I replaced mine with a new Bendix MC some 6 years ago and haven't had a bit of trouble with it.
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Team Owner
Joined: Mar 2002
Posts: 24,160
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I would suggest purchasing a hand pump vaccum bleeder, yoou will have to have one to replace the MC anyway. The old pump up and bleed does not work on a C3 vette. I replaced all the lines on my 69 and could never get the brakes to pump up or get fluid to the calipers. I was certain the Mc had failed but checked with another C3 buddy and went and got the bleeder. Start at the right rear outside, (pump till full clear fluid for a while, you will get lots of foam) then move to inside, then to the left same proceedure, then right front, then left front. My hand was sore for weeks after this proceedure. I would try this before replacing the MC, especially since the lines were separated and plugged.
1. You didn't mention if you bench bled the MC. If you don't, then you can spend a lot of time and effort pumping air around.
2. Your bleed order is wrong. C3s have a kind of goofy bleed order. It's ...
Driver Rear Inner
Driver Rear Outer
Pass Rear Inner
Pass Rear Outer
Driver Front
Pass Front
It can take you multiple laps around the car to get all the air purged if you go in the wrong order.
Thread Starter
Instructor
Joined: Mar 2006
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Well I realize after disconnecting the lines I have let air in, I just did that to test the MC. I meant I don’t see how air could have gotten in there since that is the first time it has ever had a problem or ever been tampered with. I think I'm just going to get a new MC since the pedal goes to the floor with ease even with the lines plugged. I mean it does catch but its right at the end and it wont pump up any more than that ever. The way it was leaking made it look like it was leaking inside the MC not the cap or anything, and then finding its way out.
On a side note I know bleeding a whole new MC is a pain I'm almost finished with my frame off on this 68 Yenko Camaro 427 replica and I still don’t have the brakes bleed enough..... pump a little here pump a little there..... lol. I did bench bleed that MC since it was brand new. Just beings the whole system is new it's taking FOREVER.
On a side note I know bleeding a whole new MC is a pain I'm almost finished with my frame off on this 68 Yenko Camaro 427 replica and I still don’t have the brakes bleed enough..... pump a little here pump a little there..... lol. I did bench bleed that MC since it was brand new. Just beings the whole system is new it's taking FOREVER.
Team Owner
Joined: Mar 2002
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I think I'm just going to get a new MC since the pedal goes to the floor with ease even with the lines plugged. I mean it does catch but its right at the end and it wont pump up any more than that ever. The way it was leaking made it look like it was leaking inside the MC not the cap or anything, and then finding its way out.
On a side note I know bleeding a whole new MC is a pain I'm almost finished with my frame off on this 68 Yenko Camaro 427 replica and I still don’t have the brakes bleed enough..... pump a little here pump a little there..... lol. I did bench bleed that MC since it was brand new. Just beings the whole system is new it's taking FOREVER.
Yeah, you just don't realize how much fluid is REALLY in there until you work with a dry system!
Racer
Joined: Aug 2008
Posts: 413
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From: Justin TX
I would bet you have the same issue with the new MC, spend $30 and get yourself a handpump bleeder, it will save lots time and headache. Sounds like you could use it on the Camaro too. It will pay for itself easily, just based on my personal experience.
Instructor
Joined: Sep 2008
Posts: 124
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From: Atlanta GA
From skimming through, looks like you fixed it by bleeding it out.
Just an FYI though: Sometimes the MC isn't the problem when it comes to soft/spongy brakes. My rear right tire had a leaking caliper, then I started hearing a clanking noise coming from the same wheel, and a few days later, had to replace the entire wheel arm because it broke apart in the middle of the street.
Good times
Just an FYI though: Sometimes the MC isn't the problem when it comes to soft/spongy brakes. My rear right tire had a leaking caliper, then I started hearing a clanking noise coming from the same wheel, and a few days later, had to replace the entire wheel arm because it broke apart in the middle of the street.
Good times
Race Director
Joined: May 2003
Posts: 10,956
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From: California
Read this post, Tom454 has it down pat and this may help you... http://forums.corvetteforum.com/c3-t...fo-please.html
Intermediate
Joined: Sep 2007
Posts: 40
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From: Dallas
Speed Bleeders
http://www.speedbleeder.com/