Can't get good brakes - Pontiac GTO Forum
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post #1 of 23 (permalink) Old 09-19-2015, 11:55 AM Thread Starter
 
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Can't get good brakes

I have been ill since April but able to get into my 67 GTO last week. What was wrong is not important. I installed an SSBC front disc brake conversion kit with new master and vacuum assist. With that I used a CPP model PV-2 two disc proportion valve so the front discs and rear drums work correctly. Everything was installed to the book. Master bench bled and I had to first gravity bleed the front and rears then bled them with someone on the pedal. I have a great pedal inside the car but it stops like crap. If I am going back and forth on my driveway, all is good. I took the car down my street and it slows down then stops. Not safe. I am at wits end. I called the makers and they tell me I didn't bleed the master when I did. I even used a Motive pressure bleeder, no bubbles in any wheels. I have done in my past, easily 100 brake systems. But never a conversion. Always stock swap outs. Anyone out there have experience with this? I am almost stumped. It makes no sense having pedal pressure, no air bubbles but not stopping like discs should.
Thanks
Jax
1967 GTO
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post #2 of 23 (permalink) Old 09-19-2015, 12:09 PM
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You have to drive it and seat the pads, mine did the same thing after the install.
After they were seated I cranked the proportioning valve to the point the back brakes locked up under hard braking then backed it off 2 clicks.
Now the car squats under hard braking instead of diving.
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post #3 of 23 (permalink) Old 09-19-2015, 08:08 PM Thread Starter
 
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Thanks but how do I drive it if it will not stop?
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post #4 of 23 (permalink) Old 09-19-2015, 08:52 PM
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Quote:
Originally Posted by xkeots View Post
Thanks but how do I drive it if it will not stop?
You have to yell "Whoa Goaty" when you hit the brakes.

Is your proportioning valve centered?
Turn it all the way till it stops then turn it back the other way until it stops counting the clicks or turns then go halfway.
When I did mine it didn't want to stop when I pulled it out of the shop but they started to grab after braking hard a few times.
When you brake hard do the rear drums lock up and skid?

Last edited by Goat Roper; 09-20-2015 at 12:08 AM. Reason: typo
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post #5 of 23 (permalink) Old 09-20-2015, 10:41 AM Thread Starter
 
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My proportioning valve is self adjusting. It's a PCC PV2.
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post #6 of 23 (permalink) Old 09-20-2015, 10:43 AM Thread Starter
 
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Sorry it's a CPP PV2 self adjusting.
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post #7 of 23 (permalink) Old 09-20-2015, 11:20 AM
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Maybe the valve is defective, if you have a solid pedal and no air in the lines and the calipers are functioning there is no reason the car shouldn't stop.
Can you feel the power assist in the pedal from the booster?
You may not have enough manifold vacuum.
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post #8 of 23 (permalink) Old 09-20-2015, 03:46 PM Thread Starter
 
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I am getting at least 18psi to the booster. When running the pedal feels fine. Just not stopping as it should. If I am doing 25mph and I hold the brake, it slows down for about 200 ft then stops.
Not cool. Master was bled and lines have no air bubbles.
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post #9 of 23 (permalink) Old 09-20-2015, 05:42 PM
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How about the linkage that goes from the pedal into the master?
Is it adjustable and is it bottoming out before it gets full stroke to the master?
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post #10 of 23 (permalink) Old 09-20-2015, 05:55 PM
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I would also check the brake booster check valve, if the check valve is not working or leaking at idle you'll have good vacuum and while driving the vacuum in the booster goes to zero. If your not storing vacuum that may explain why you can't stop. Also, is your cam stock?

Randy


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