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No pedal after master cylinder replacement

 
Old 05-16-2019, 03:18 PM
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Runningwild
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Default No pedal after master cylinder replacement

1974 C3. Master was replaced and system was power bled numerous times. I took it home jacked up the rear. Wire in the 2 holes. Level bubble towards windshield. Now to bleed the 2 bleeders on the master cylinder should the car be up in the air in the rear or level on the ground. Still no pedal. Thanks. Tom
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Old 05-16-2019, 03:30 PM
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Easy Mike
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FWIW: Master cylinder must be bled first before you start on the calipers.
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Old 05-16-2019, 03:43 PM
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Runningwild
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Yes. I know. I was referring to the 2 bleeders on the master cylinder. I want to bleed them next before I start on the calipers.
Should the car be level or rear end up to finish the master cylinder.
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Old 05-16-2019, 03:46 PM
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The Punisher
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level. did you bench bleed the master before install?
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Old 05-16-2019, 03:57 PM
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Runningwild
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I had it installed at the local corvette club shop. I would think he would know to do that. Of course I told him about raising the rear of the car to get the air out of the master.
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Old 05-16-2019, 08:03 PM
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Originally Posted by Runningwild View Post
Yes. I know. I was referring to the 2 bleeders on the master cylinder. I want to bleed them next before I start on the calipers.
Should the car be level or rear end up to finish the master cylinder.
To bleed the MC while on the car like this
https://www.corvetteforum.com/forums...-cylinder.html

Now you need to see air bubbles coming from the bleed holes . It may take a good 30 minutes before all the air is out. Press the pedal very slowly and watch for air or fluid coming from the bleed holes.

Also make sure the bleed holes are not plugged in any way. You will know this by a quick push on the pedal it should shoot brake fluid up in a stream. ( Please take care that fluid doesn't splash on your car ).

Once you feel the MC is free from air, then I usually connect a tube from the front driver caliper bleed screw back into the MC. Pump the pedal until you get no air in the line.

Then once you are ready to bleed the calipers you can lower the car. Bleed the longest brake line to the shortest brake line. Make sure you bleed each bleed screw, usually 2 per caliper.
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Old 05-16-2019, 10:01 PM
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I had the same problem. I changed the calipers, lines and master. Bled the brakes for a month, every way known to man. It turned out the rod that goes into the rear of the master needed adjustment. The plunger in the back of the new master was a little different. I adjusted the rod and I had brakes. Heres what I went thru.



https://www.corvetteforum.com/forums...bleeder-2.html

Last edited by 540 vette; 05-16-2019 at 10:02 PM.
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Old 05-16-2019, 10:17 PM
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Thanks guys. Iíll try this weekend. No power booster. No power brakes, steering or air. Basic 74
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Old 05-17-2019, 02:19 PM
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Originally Posted by Runningwild View Post
1974 C3. Master was replaced and system was power bled numerous times. I took it home jacked up the rear. Wire in the 2 holes. Level bubble towards windshield. Now to bleed the 2 bleeders on the master cylinder should the car be up in the air in the rear or level on the ground. Still no pedal. Thanks. Tom
How did you bring it home with bad brakes? Drive it?
Define No Pedal - goes to the floor and does not stop, or has mush brakes.

Define Power Bled. Was it pressure from the master, or using a mighty vac at the calipers or.......?
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Old 05-17-2019, 03:18 PM
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Yes. Drove it home with no brakes. Only a mile. They hooked up a pressure bleeder to the master after replacing it and it pushed fluid out the calipers. They did it numerous times. Canít build pressure by pumping the brakes. Pedal goes to the floor. Only minimum pedal resistance. I bleed the master as described with level Ext. Now Iíll move on to the calipers. Then Iíll check the engagement rod. Hopefully this will work. Tom. Thanks for all the info. Appreciate it.
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Old 05-17-2019, 03:56 PM
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Fredtoo
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I would check to see if the master is defective.

You need to make a plug for where the brake lines go into the master.
With those sealed off, you should be able to bleed the master and get a ROCK hard pedal.
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Old 05-18-2019, 01:26 PM
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Tampa Jerry
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Is it possible the shop installed the wrong M/C? There is a difference between power and manual. Jerry
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Old 05-18-2019, 03:28 PM
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Iíll check. They are ďsupposed ď to be good but now Iím not sure. My race car engine builder has done tons of vetted and he will come to up to the house if I canít figure this out. Iíll check the invoice to see the part number. Thanks
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Old 05-18-2019, 04:14 PM
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Originally Posted by Tampa Jerry View Post
Is it possible the shop installed the wrong M/C? There is a difference between power and manual. Jerry
A power brake master has a bigger bore, it would give a really stiff pedal.
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Old 05-18-2019, 06:44 PM
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Did you check the rod. Or you can adjust the clevis at the brake pedal if you can't at the master.
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Old 05-18-2019, 06:44 PM
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Originally Posted by Fredtoo View Post
A power brake master has a bigger bore, it would give a really stiff pedal.

No it wouldn't.
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Old 05-19-2019, 06:33 AM
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Originally Posted by Fredtoo View Post
A power brake master has a bigger bore, it would give a really stiff pedal.

This!
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Old 05-19-2019, 08:35 AM
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Originally Posted by 540 vette View Post
No it wouldn't.
Why not?
It has a bigger bore (1-1/8 vs 1") and moves more fluid per distance of pedal travel.
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Old 05-19-2019, 10:11 AM
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Originally Posted by Fredtoo View Post
Why not?
It has a bigger bore (1-1/8 vs 1") and moves more fluid per distance of pedal travel.

It wouldn't give a stiff pedal like a bad master. It would stop harder. I have swapped them when I had the problem and honestly didn't know the difference. But that isn't the issue here as the OP has bled the brakes and has no pedal. If the plunger in the master is different than the original he will never get a pedal unless he checks and adjusts the rod in the booster.

Last edited by 540 vette; 05-19-2019 at 10:14 AM.
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Old Today, 04:02 PM
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Funny you guys mentioned that it might be the wrong master cylinder! I texted the shop and they think they ordered the wrong one. I’ll check it out this week.
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