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Help! Master cylinder:

401KVet

Well-known member
Joined
Nov 2, 2008
Messages
330
Location
Port Allen, LA
Corvette
1980 L82 Coupe, Black
This is my problem. I'm trying to bleed the master cylinder, but cannot get any fluid out of either side on the rear. The front seems ok so for. All air out. Now my story from the beginning, short as possible.
I'm replacing all calipers, lines and hoses and pads. I did have the brake lines, hoses, and calipers all OFF. So all brake lines were OPEN. Now I was hoping to let gravity take it's course and slowly flush the old fluid out. I first used a turkey thingee to sucked all of the old fluid out of the master cylinder, and then filled it with fresh. Now full again, I was getting NO fluid coming out of any of the open brake lines. After a day, I clamped the master cyl. cap back down and then pumped the brake pedal a few times. Some came out of the LR, very little out of the LF, and the other's none. So still wanting to flush the old fluid out of the lines before installing the new calipers I bought from Vette Brakes, I called them for some hep. They suggested that I brake both lines going into the Master Cylinder and blow air throw the lines to force the old fluid out. So with my air compressor that's what I did, and it seemed to work. Again, all the old calipers and old brake hoses and lines are OFF at this time. Yes, I should have flushed first, before taking all off. SO, now that I have everthing togeather and almost finished, I can't get anything out of the rear. I was going to replace the emergency brakes, but after starting of one side, I decided I would do it later after making taking some classes. LOL So I took all of the brake hardware off of both sides. I'm sure this has nothing to do with my bleeding problem. Anyhow, does anyone have any suggestions on what to try? Do I now have a bad master cylinder?? The car has been sitting up for over a year and a half. As for as the way I was bleeding the brakes, the old way, one pumping and the other at the caliper. Help please..
 

Yep, it's me. This has been a long drawn out process/repair. Working on it only when I'm feeling up to it, and able. My health is not that great. So since that last post, I now have everthing installed, and NOW the problem is not being able to bleed the rear down. My friend/mechanic that's helping me with it wanted me to push down on the brake pedal hard, which was after we started having the stated problem. He said to stand on it. When I did we heard some type of pop that sounded like it came from under/under the firewall somewhere. He said that was probaly air releasing from the proportioning valve and he thought then all would be ok, but not. That did not make much sense to me, but he knows more than I. Before this happen we had already done the front, so I did have some sort of pedal. He now said's I need a new master cylinder. But before I order one I wanted to see what you guys thought about it and maybe would have something I could try before I buy a master cylinder... Thanks.
 
The 'pop' was probably the piston in the proportioning valve as your friend mentioned. Is the brake light 'now' illuminated on the dash?

Reading your other thread, the master cylinder has to be bled (lines detached) before attempting to bleed the rest of system. Not sure you did that.
 
The 'pop' was probably the piston in the proportioning valve as your friend mentioned. Is the brake light 'now' illuminated on the dash?

Reading your other thread, the master cylinder has to be bled (lines detached) before attempting to bleed the rest of system. Not sure you did that.

This is the same master cylinder that I have had on the car, not a new one. So are you saying I need to take it off and bench bleed it?? Then reinstall and finish bleeding the lines and calipers? The car is still up on jackstands and have not ran it yet, so i can't say about the brake light.
 
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What do you think about using some type of anti-squeal compound on the back of the pads? Does the stuff really work? The pads I went with is Wagner's ceramic. The best pair they offered for a Vette.
 
I had my go 'round with the brakes earlier this year. A new Wagner master cylinder is about 40 bucks if you are not concerned with numbers. I ended up pushing a couple of quarts of fluid thru the system before I got all of the air out. Check the calipers for leaky seals. This is what burned me (see 81 Stingray soft brakes).

I have not used the disk pad membrane and have had no issues with noise, but I am still using organic pads. Ceramics are definitely on my list. I have used it on other vehicles with good results.
 
I replaced the power booster and master cylinder new about 3 years ago. Hope there's no problem there.
 
What do you think about using some type of anti-squeal compound on the back of the pads? Does the stuff really work? The pads I went with is Wagner's ceramic. The best pair they offered for a Vette.

Stock pads require no anti-squeal compound. No need for ceramic pads, organic do a great job.
 
Update:

Due to health reasons, this is still going on and I just got back on it this past Friday. This is where I'm at now. I got all the new calipers, brake pads, hoses and brake lines installed. Same master cylinder and booster that was replaced about 4 years ago. I had trouble bleeding the lines at the calipers. Two people, one pumping the pedal and the other at the caliper. Nothing would come through. So I purchased a Motive power brake bleeder and used as instructed. I got all the lines to flow really well with a lot of air bubbles coming out. So all that is done now. Now I capped the master cylinder and starter the car. The brake light came on right away. I pressed the brake pedal and the pedal was really hard. I put it in gear and had just enough brakes to stop the roll. Pedal is very hard. After a couple of hours I did the booster test. Holding my foot on the brake pedal, I started the car and the pedal went down 2 or 3 inches. I read if that happens the booster should be good. I went outside a little earlier and without starting the car I pumped the brake pedal and it's hard right off the bat. I have not checked the booster check valve yet. I was going to look at that tomorrow. Also, I question about the bleeding sequence. I had been told to start with the furthest from the MC, which I would think would be the right rear, then left rear, then right front and left front. And on the rear to start with the inner bleeders. But my 1980 Corvette service manual said's to go with the left rear, then right rear, left front and then the right front. Which is correct? I'm open to any help or suggestions. Thanks..
 
Interesting, I've always been told the same as you about the bleeding sequence, but my manual says the same as yours does. Not sure which to go with now...
 
Did you bench bleed the M/C?

No not yet. I was heading in that direction. I went to Napa yesterday and bought a bench bleed kit. I did not have a chance to do anything today on it. But a question: The master cylinder never was taken OFF. I guess to bench bleed it I will have to do so. Could this be the problem even if the MC was not removed? Someone told be if the MC is the problem, it won't cause a hard pedal. It would cause a spongy pedal. ?? Your thoughts on that.. I willing to try just about anything right now.
 
See post number 4 way up above.
Be sick all week. Have not had a chance to do anything. Question: Since the M/C is already mounted, is it possible to bleed the M/C while it is on the car, using the bleeder kit, with one person at the cylinder and another pumping the brake pedal? Wouldn't that be the same as doing it with a screw driver in a vise??? Thanks
 
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Thats the way I've always done it. its easier to press your foot than push a screwdriver.
So if I understand you right, you have bled the master cylinder with it mounted on car using one of those brake bleeder kits, by pumping the brake pedal ? Then fill with fluid, cap it, and reattached the 2 brake lines? And then bleed all lines through the calipers? I thought this would work, but I have never heard of anyone doing it this way. All I've heard is bench bleed it before mounting using a vise.
 
Thanks for the help:

In case anyone hasn't figured this out yet, I am no mechanic..lol Thanks for all the help..
 

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