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[ChaosweaveR]

ATTN: old school guys (brake help needed)

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Having some issues with the shop's 95 Caprice LT1 wagon. Last Thursday, the car lost it's brake pedal, but did not spring an external leak.

We've checked all four corners for leaks, bled the brakes a few times, but the pedal still goes to the floor. We're thinking it's a master cylinder, but we encountered an interesting result after trying one last trick this morning.

Putting a vicegrip on each brake hose, the pedal hardened up again, even while running. One at a time, we first tried taking off the fronts. Pedal felt normal. But the rears made it sink to the floor and give us the spongy pedal again.

The rear drums have been cleaned and adjusted, wheel cylinders are not leaking, none of the metal lines are leaking and they're holding pressure and there's absolutely no air in the system.

We're at a loss here, any ideas?

Added: the Caprice has a dual reservoir master cylinder, which is the front and rear?

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Best guess...master. Blowby on pump seals. Will add some pressure to system, not enough to function properly. Pinching off lines shortens the total system and eliminates the extra movement of calipers = more pedal. Can't think of any brake system 60's up that doesn't have front /rear reservoir. Usually front front, rear rear. Most can follow a line to figure that one out. One last thing to check is the valve in the proportioning valve. Usually in the front, has a rubber cap. Push in and hold, have someone pump up brakes and hold, then release valve, then the pedal. Rarely do these go bad, something to check.


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Thanks for the tip. We'll be checking the proportioning valve next.

I didn't realize that Eddie (the guy I'm working with) bled the rears from the lines out back since he wasn't able to crack lose the bleeders. Soon after I made the post we took out the wheel cylinders and got the bleeders free, some of the sliders on the shoes were seized as well. That's all freed up, but I was busy with the race trailer, Eddie was working on a car when I got back there but he hasn't checked for a pedal feel yet since some cars came in.

I relayed the info to him, he's going to check that. I'll update after some more checking and adjustments.

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A very rare situation happened to be with my old '73 Lemans. I am not certain how it happened but it did. Something contaminated the brake fluid and the containment destroyed the seals in the master cylinder and the top, allowing air in and no pedal.



So test the brake fluid or replace it entirely. The brake fluid might be getting weak.



I agree with JUSTA6 on his analyisis too.



Also, if you suspect the lines to be dirty (based on what you see), try to blow out the lines with compressed air and then re-bleed the lines. On my '81 Phoenix, I had an inner brake tube collapse and it would not allow fluid to pass through on the passenger front. So I was getting no braking from that side of the car. The tech had to replace the bad line with a new one since, after 100 lbs of pressure put to it, it would not clear out.



Have you checked the brake booster to see if it is holding vacuum properly?


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We bled the system a few times, I'd say it's clean for the most part. We weren't having pressure issues at all (especially bleeding it again with the drums freed up)

There's vacuum pressure for sure.

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Vacume only makes it easier to push the pedal. Has nothing to do with system function. I'm ol skool N still use 2 person bleed, but never start the car to do so. Actually gives a false sense of the pedal comming up as you bleed each corner. Was the front calipers replaced? Or did it JUSTA go bad? If both calipers were installed on the wrong side, your bleeders will be at the bottom and no way, power bleeding or not to get all the air out of the system.


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Front calipers are fine, pistons retract with no issues. We did the two person system bleeding (the way I was taught anyway).

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My first inclination says it is the master cylinder - perhaps it has developed a crack or internal leak somewhere and may need to be replaced.



One other thing I can think of, the flex lines between the frame and the rear end or the frame and each front disc caliper, could they be worn out and simply swelling (internally) and thus it does not force the fluid into the wheel cylinders or calipers? Perhaps the flex lines may need replacing.


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Vacume only makes it easier to push the pedal. Has nothing to do with system function. I'm ol skool N still use 2 person bleed, but never start the car to do so. Actually gives a false sense of the pedal comming up as you bleed each corner. Was the front calipers replaced? Or did it JUSTA go bad? If both calipers were installed on the wrong side, your bleeders will be at the bottom and no way, power bleeding or not to get all the air out of the system.

My point with the booster is that it helps to increase the pressure in the system. If it failed, then someone would have to stand on the brake pedal to try to compensate. I agree it would not prevent the system from working. It would appear that something has failed though. I just want to be thorough.

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Good point on the flex lines Frosty. Wasn't even thinkin about that! Your right again on the vacume. Somebody would be using 2 feet on the brake pedal.

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Fluid was another good point you see often, but it happens. Cloudy at all...replace.

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This is crazy, I can't edit a post here anymore, Can't reply with a quote. I missed the DON'T see very often on the brake fluid. I can't insert smilies anymore as well. WTH?

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The struggles of the one-armed man perhaps?



BTW - Sometimes I have issues editing too if I am using Internet Explorer, which is why I use Google Chrome as my browser at home. At work, its IE or nothing I'm afraid.


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The edit/quote buttons are run by javascript/jquery script, if you are using an older browser (I think it's IE8 or lower) than you may have some issues acting on these items as we do not support these older browsers as they hit end of life in the tech world.



Sometimes IE is just quirky as well, if you can help it I would suggest using Google Chrome or Mozilla Firefox.


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The edit/quote buttons are run by javascript/jquery script, if you are using an older browser (I think it's IE8 or lower) than you may have some issues acting on these items as we do not support these older browsers as they hit end of life in the tech world.

Sometimes IE is just quirky as well, if you can help it I would suggest using Google Chrome or Mozilla Firefox.

My work PC is running IE 8. I find Chrome a lot faster than IE - even IE9 & 10.

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My work PC is running IE 8. I find Chrome a lot faster than IE - even IE9 & 10.

Yup, IE is the one MS product I despise and wish would die a fiery death lol. Chrome and Firefox all around are the 2 best browsers.

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:agreed:


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I would lean on the master cylinder as well sounds like a rubber seal went bad on the rear most reservoir part of the piston. Also check the rear flex line. Have someone pump the brake pedal and look at the rear line. Ensure that it is not swelling up like a balloon. This is caused by the re-enforcing bands in it by letting go. It will not be easily seen and may take a few minutes.


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This is an old computer, I'm sure I'm using Explorer. Sounds like the the root of many probs lately.

Ok....here come the jokes! How do I switch to chrome? There's no kid in sight. LOL

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This is an old computer, I'm sure I'm using Explorer. Sounds like the the root of many probs lately.

Ok....here come the jokes! How do I switch to chrome? There's no kid in sight. LOL

http://www.google.com/chrome

Go to link -> Click Download -> It will download -> Click Run -> it will install -> Open Google Chrome once installed :)

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WELP, it was the master cylinder. The pedal actually came back after we bled the rears again and freed up the rear drums, but Eddie was too hard on the brakes the other day and the seal must have finally went out. Changed it today, pedal is better than it ever was.

Thanks for the advice, certainly helped out keeping the old boat going.

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I love them B-bodies. Glad we could help.


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http://www.google.com/chrome

Go to link -> Click Download -> It will download -> Click Run -> it will install -> Open Google Chrome once installed :)

....and if you have any other problems with it, you call Frosty and meet him at a mutually agreeable Tim Horton's or McD's location (that has Wi-Fi) and we fix it. You're buying.

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LMAO... I'm not carrying this whole stack, monitor, keypad anywhere. Couldn't if I wanted to. It's not a laptop. LOL

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You are obviously getting ready for the 20th century, technologically speaking.



Case in point:



Old GTO


Old Sunbird


Old flip phone


Old "desktop" computer


Q.E.D. - Old "guy"


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