Brake Pedal clevis location question - Chevelle Tech
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post #1 of 21 (permalink) Old Sep 18th, 16, 4:23 PM Thread Starter
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JOHN C
 
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Angry Caliper is dragging

67 Chevelle with factory 4 piston calipers all new. I bled the brakes and the front wheels spin
free until I apply the brake pedal then they are stuck and dont turn,

If I crack open the bleeder and let some air and fluid out and tighten it back up then the front wheels will
turn again. All my brake lines are new including the rubber hoses. Calipers are rebuilt and the pistons
are not stuck. This is a power front disk brake 67 Chevelle

Any ideas on whats causing this? thanks
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post #2 of 21 (permalink) Old Sep 18th, 16, 7:25 PM
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Levon
 
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Re: Caliper is dragging

Did you do the master cylinder at the same time? Is the pedal and master cyl piston retracting all the way?

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post #3 of 21 (permalink) Old Sep 18th, 16, 8:41 PM
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Re: Caliper is dragging

My 66 I had the rod adjusted a little too long. Driving around was fine but when it got hot it would tighten up and not release after hitting the brakes. I shortened it up a bit and its been working fine since. My 66 is running later chevelle disc brakes and mid 70s chevelle manual mc. Jim
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post #4 of 21 (permalink) Old Sep 18th, 16, 11:07 PM
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Denny
 
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Re: Caliper is dragging

Usually, it is because the m/c doesn't fully retract to its resting place. To verify this, open m/c lid and apply gently the brakes. You should see 2 little geysers in the m/c. If you don't, or see just one, your m/c doesn't retract to its proper resting place.

It is often because you have the wrong booster push rod, or your pedal/booster doesn't retract correctly.
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post #5 of 21 (permalink) Old Sep 18th, 16, 11:52 PM
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Re: Caliper is dragging

What Jim and Denny said.

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post #6 of 21 (permalink) Old Sep 19th, 16, 11:54 AM Thread Starter
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JOHN C
 
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Question Brake Pedal clevis location question

On a 67 Chevelle with front power disk brakes and a 4 speed there are 2 holes in the brake pedal
for the clevis to attach to. One is higher up and one is a bit lower. Can anyone with a 4 speed disk brake Chevelle tell me which is the correct hole to attach the clevis to. Im using the lower and my front wheels
lock up everytime I hit the brakes. Cracking the bleeder frees it up. Many threads point to the pushrod being in the wrong position and also to rod adjustment and proper play. Im wondering if I just have the damn thing in the wrong hole.

many thanks
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post #7 of 21 (permalink) Old Sep 19th, 16, 11:58 AM
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Re: Brake Pedal clevis location question

Manual brakes the top hole is used and with power brakes use the lower one. Which bleeder are you opening t relieve pressure?

it is not whether you win or lose but how you place the blame
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post #8 of 21 (permalink) Old Sep 19th, 16, 12:44 PM Thread Starter
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JOHN C
 
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Re: Brake Pedal clevis location question

thanks - Im opening the bleeder on the front caliper to unstick the brakes. Soon as I pump the brakes again the front wheels get real hard to turn -- Im kinda stumped at this point. Im using the lower hole on the brake pedal and I
had to install an extension to my booster rod because the clevis did not reach the brake pedal. Other than that its all stock.

the car was an automatic and I changed to a 4 speed. So the pedal setup is now that of a 4 speed. I got the
brake and clutch pedal setup out of another 67 Chevelle. The booster is the original I had it rebuilt-- the master is the
correct one with the deep bore and it is new. This is making me really frustrated, and setting me back in finishing the car....
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post #9 of 21 (permalink) Old Sep 19th, 16, 12:46 PM
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Re: Brake Pedal clevis location question

Sounds like the rubber flex hose is bad. They can break down internally and block the return flow of fluid causing the brakes to be locked. I suggest replacing both front and the one in the rear. Then bleed the brakes. Should solve the problem.

it is not whether you win or lose but how you place the blame
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post #10 of 21 (permalink) Old Sep 19th, 16, 1:07 PM
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gary
 
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Re: Brake Pedal clevis location question

Do you have free play in the push rod? You need some to release the pessure. Are both front wheels locking up?
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post #11 of 21 (permalink) Old Sep 19th, 16, 1:17 PM
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Hank
 
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Re: Brake Pedal clevis location question

How does your brake booster and mc sit. On an angle or level. I know on angled setups the clevis goes to the bottom hole but I'm not sure if it would go to the bottom hole if it is level. Whatever hole it ends up in make sure you have a little free play before the pedal puts any pressure on the mc. Maybe someone else with a 67 power brake car can chime in on this.

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post #12 of 21 (permalink) Old Sep 19th, 16, 1:45 PM
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Denny
 
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Re: Brake Pedal clevis location question

Stop starting new thread about this problem. This is your third one (#1 and #2) and it becomes hard to follow what you've done and what you have not done already. (Philip wouldn't have suggested the rubber hoses if he knew you had new ones)

This is usually a very simple and common problem of having a booster push rod with the wrong adjustment. The first test to do in troubleshooting this problem is a very simple and easy test I already asked you to do in an earlier thread:

Quote:
Originally Posted by Jack Action View Post
Usually, it is because the m/c doesn't fully retract to its resting place. To verify this, open m/c lid and apply gently the brakes. You should see 2 little geysers in the m/c. If you don't, or see just one, your m/c doesn't retract to its proper resting place.
Before we continue, what is the result of this test?
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post #13 of 21 (permalink) Old Sep 19th, 16, 4:26 PM Thread Starter
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JOHN C
 
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Re: Brake Pedal clevis location question

Okay thanks all for replying - I really appreciate all of your time and advice. I read many helpful suggestions.
After more than a week of studying this problem and reading up I decided to do one of the things I read in one
of the threads - some of the things I read to do were to trim the pushrod that comes out the front of the booster and goes into the back of the mc.
Others said they put a few shims between the mc and the booster. So I tried the shim method because its quick and
less of an invasive procedure. I also checked and re-adjusted my clevis and rod under the dash. I made sure I had some pedal play as suggested. Well Im very happy to report that the shims solved the problem.

I can pump the brake pedal now and the front tires spin as they should-- a tad stiff but everything is new and car has not yet been driven. They do not lock up anymore. Also the pedal now has a much better feel to it when I apply the brakes than it did before I put the shims, it had a clunky feel to it that was not smooth before. Now it feels perfect.
Im not crazy about using shims because there is now a space between the mc and the booster - I may trim down the pushrod at some point, but for now Im leaving it as is. Ive got to move on to the next thing to get the car running before
the real cold weather comes in. For now the brake dilemma is over.
THANKS TO ALL WHO PITCHED IN !! YOUR HELP IS APPRECIATED.
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post #14 of 21 (permalink) Old Sep 19th, 16, 5:37 PM
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Re: Brake Pedal clevis location question

As Jack said one thread for a question is plenty. Multiples could result in all of them being deleted. We offer help for free but scattering the same question all over the forum wastes a lot of the members time.

Shimming the master is a test leaving it that way is not advised.
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post #15 of 21 (permalink) Old Sep 19th, 16, 8:52 PM Thread Starter
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JOHN C
 
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Re: Brake Pedal clevis location question

I agree and Im working on a permanent solution, thanks again !
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