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brake pedal hard, then soft

Old 12-07-2018, 08:13 AM
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autoalain
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Default brake pedal hard, then soft

Folks, pedal on my 71 is rite at the top after caliper rebuild and new master, adjusted rod also, then start car and it goes down 1/2 way, just to be sure I bleed brakes
again with the special tool that sucks the oil, start car and pedal goes dowm, this does not make sense to me, i'm an old fart and must have missed something, it
is power brakes and good vacume 18 lbs on engine, pls help...Thanks Mike.
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Old 12-07-2018, 10:06 AM
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The Punisher
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Did you bench bleed the master cylinder ?
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Old 12-07-2018, 10:40 AM
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69autoXr
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Sounds like normally functioning power brakes to me. Did you drive it?
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Old 12-07-2018, 11:20 AM
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carriljc
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Get a pressure bleeder. Or make a pressure bleeder... depending on how much of a hurry you are in.

https://www.corvetteforum.com/forums...y-version.html

Last edited by carriljc; 12-07-2018 at 11:22 AM.
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Old 12-07-2018, 11:31 AM
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cardo0
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Originally Posted by The Punisher View Post
Did you bench bleed the master cylinder ?
Yes you need to bench bleed the m/c at horizontal - no angle. It should have been in your instructions with the m/c.
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Old 12-07-2018, 12:06 PM
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MelWff
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in addition to the previous comments about bleeding the master, what sequence did you use to bleed the brakes and did you use anything to tap the calipers while bleeding to dislodge air bubbles?
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Old 12-07-2018, 01:01 PM
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autoalain
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Originally Posted by MelWff View Post
in addition to the previous comments about bleeding the master, what sequence did you use to bleed the brakes and did you use anything to tap the calipers while bleeding to dislodge air bubbles?
Yep bleed master on desk, started bleeding at r/h rear, jacked car up high at front, used proper tool that sucks from caliper, have NOT tried on the road yet, pedal is rite
at top when car not running, do not think air, rebuilt master also. Thanks
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Old 12-07-2018, 06:31 PM
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why did you jack the car up high in the car should be level, rear calipers have two bleed screws each, rr, lr, rf, lf is the sequence. Have always gravity bled and have never had a problem.
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Old 12-07-2018, 07:17 PM
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Originally Posted by cardo0 View Post
Yes you need to bench bleed the m/c at horizontal - no angle. It should have been in your instructions with the m/c.
I disagree on the horizontal. The nose of the MC should pointed up for a few strokes while the MC is in bench vise. Then a few strokes with the nose down, then several strokes at level.
Without tilting the MC around is exactly why bubbles get trapped in bore of the MC. This is why it seldom bleeds & works well on a level car. That trapped bubble is also why pressure bleeders are so successful at removal of the last bubble.
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Old 12-07-2018, 07:33 PM
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cagotzmann
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Originally Posted by autoalain View Post
Folks, pedal on my 71 is rite at the top after caliper rebuild and new master, adjusted rod also, then start car and it goes down 1/2 way, just to be sure I bleed brakes
again with the special tool that sucks the oil, start car and pedal goes dowm, this does not make sense to me, i'm an old fart and must have missed something, it
is power brakes and good vacume 18 lbs on engine, pls help...Thanks Mike.
You will get info on bench bleed the master cylinder , but will you let you know you can do this on the car also.

Read this.
https://www.corvetteforum.com/forums...-cylinder.html

Bench Bleeding is a good start to shorten the time for on car bleeding, but on car bleeding will insure you get all the air out of the MC.
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Old 12-07-2018, 08:47 PM
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Big2Bird
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I use the Motive pressure bleeder. Fast, visual, and once you see all the doo doo you can flush out, you will never do it any other way.
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Old 12-07-2018, 10:53 PM
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Originally Posted by 69autoXr View Post
Sounds like normally functioning power brakes to me. Did you drive it?
Yep! Sounds like it to me too.
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