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04-19-2025, 12:39 PM
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#1 |
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Burnouts are therapeutic
Join Date: Jun 2007
Location: lancaster, south carolina
Posts: 858
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brakes locking up
hey i have a new build , it's a 70 with cpp front power disc brake conversion . it looks up all 4 wheels , if i crack the front bleeder valve it releases. it does ok for a minute then locks up. I'm thinking the check valve is sticking in the master cylinder? any ideas on whats causing it?
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1969 CHEVELLE SS 1972 C10 ALMOST DAILY DRIVER 1968 C10 RUSTBUCKET (MISSION IMPOSSIBLE) 1972 PONTIAC LEMANS CONVERTIBLE (WIFE'S CAR) "My wife and I were happy for twenty years. Then we met." - Rodney Dangerfield "The difference between genius and stupidity is that genius has its limits." - Einstein |
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04-19-2025, 02:54 PM
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#2 |
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Senior Member
 Join Date: Feb 2022
Location: Ca
Posts: 1,026
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Re: brakes locking up
Pin between booster and master is too long. Master needs to fully return home to release completely. Common problem with today manufacturering tolerance.
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04-19-2025, 02:58 PM
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#3 |
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Senior Member
Join Date: Feb 2022
Location: Ca
Posts: 1,026
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Re: brakes locking up
Or brake pedal spring not pulling pedal all the way bach. Pull up with your foot after braking and see if it helps
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04-19-2025, 03:19 PM
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#4 | |
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Burnouts are therapeutic
Join Date: Jun 2007
Location: lancaster, south carolina
Posts: 858
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Re: brakes locking up
Quote:
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1969 CHEVELLE SS 1972 C10 ALMOST DAILY DRIVER 1968 C10 RUSTBUCKET (MISSION IMPOSSIBLE) 1972 PONTIAC LEMANS CONVERTIBLE (WIFE'S CAR) "My wife and I were happy for twenty years. Then we met." - Rodney Dangerfield "The difference between genius and stupidity is that genius has its limits." - Einstein |
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04-19-2025, 04:07 PM
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#5 |
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Registered User
Join Date: Mar 2017
Location: yucca valley
Posts: 318
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Re: brakes locking up
I had the same problem with a CPP master cylinder. After a few minutes, it would lock the brakes up on all four wheels start smoking the brakes, replace the master cylinder problem solved.
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04-19-2025, 08:20 PM
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#6 | |
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Burnouts are therapeutic
Join Date: Jun 2007
Location: lancaster, south carolina
Posts: 858
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Re: brakes locking up
Quote:
__________________
1969 CHEVELLE SS 1972 C10 ALMOST DAILY DRIVER 1968 C10 RUSTBUCKET (MISSION IMPOSSIBLE) 1972 PONTIAC LEMANS CONVERTIBLE (WIFE'S CAR) "My wife and I were happy for twenty years. Then we met." - Rodney Dangerfield "The difference between genius and stupidity is that genius has its limits." - Einstein |
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04-19-2025, 08:23 PM
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#7 |
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Registered User
Join Date: Mar 2017
Location: yucca valley
Posts: 318
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Re: brakes locking up
I just ordered it from summit racing for the replacement.
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04-19-2025, 08:45 PM
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#8 |
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Ram-A-Lam-A-Ding-Dong
Join Date: Jan 2013
Location: Simi Valley, CA
Posts: 11,903
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Re: brakes locking up
Sounds like thermal expansion issues. As a temporary measure, put some 1/8" thick washers or shims (easier) between the booster and the master. If that takes care of the problem, you just need to put more play in the braking system. Best place to start is at the pedal, and I should have asked that question first- how much play do you have when pushing on the brake pedal? It should move about 3/8" before the brakes begin to actuate.
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~Steven '70 Chevy 3/4T Longhorn CST 402/400/3.56 Custom Camper Simi Valley, CA |
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04-21-2025, 12:57 PM
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#9 |
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Senior Member
Join Date: Feb 2022
Location: Ca
Posts: 1,026
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Re: brakes locking up
You can shim as a temporary.
This will assist with getting the pin the correct length. https://a.co/d/9OWRNCz |
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04-22-2025, 10:58 AM
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#10 |
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Senior Member
Join Date: Nov 2013
Location: East Tennessee
Posts: 2,408
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Re: brakes locking up
There should be 1/32"-1/16" clearance between the booster push rod and the MC piston.
A tool like PbFut's link, is what you need to set the clearance.
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1967 C10 Step side 1968 C10 Step side 1970 Chevrolet K/5 Blazer ............. 
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05-20-2025, 07:58 PM
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#11 |
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Burnouts are therapeutic
Join Date: Jun 2007
Location: lancaster, south carolina
Posts: 858
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Re: brakes locking up
adjusting the pin seems to have one the trick. thanks guys
__________________
1969 CHEVELLE SS 1972 C10 ALMOST DAILY DRIVER 1968 C10 RUSTBUCKET (MISSION IMPOSSIBLE) 1972 PONTIAC LEMANS CONVERTIBLE (WIFE'S CAR) "My wife and I were happy for twenty years. Then we met." - Rodney Dangerfield "The difference between genius and stupidity is that genius has its limits." - Einstein |
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