The 1947 - Present Chevrolet & GMC Truck Message Board Network







Register or Log In To remove these advertisements.

Go Back   The 1947 - Present Chevrolet & GMC Truck Message Board Network > 47 - Current classic GM Trucks > The 1967 - 1972 Chevrolet & GMC Pickups Message Board

Web 67-72chevytrucks.com


Reply
 
Thread Tools Display Modes
Old 07-18-2013, 11:41 PM   #1
Slammed66
Needs a Big Block
 
Slammed66's Avatar
 
Join Date: Oct 2003
Location: Red Deer , Alberta
Posts: 1,198
Help!!! Brakes apply themselves

I just converted a 68 3/4 ton. To a half ton

I used a 86 pickup front end.
New everything

Master cyl
Booster
Brake lines
Calipers


It's drives for a while then the brakes seem to stay
On and then get worse
The pedal gets very firm.
And you can drive , the brakes are ON.
It releases after sitting and cooling down.


I'm running ideas through my head like
Do I have the pedal rod out of adjustment, ? That would cause drag but would they come on and stay on?

Do I have a bad prop valve ??

The booster and master are a kit from cpp

This thing is driving me nuts
Posted via Mobile Device
__________________
1964 Short box
On dropmembers and billets
1962 Suburban family cruiser
1972 K10
Slammed66 is offline   Reply With Quote
Old 07-18-2013, 11:45 PM   #2
IntegratedTJ
Registered User
 
IntegratedTJ's Avatar
 
Join Date: Jul 2013
Location: Vallejo, California
Posts: 71
Re: Help!!! Brakes apply themselves

This is a shot in the dark but where do you have the vacuum for the booster attached?
IntegratedTJ is offline   Reply With Quote
Old 07-19-2013, 12:00 AM   #3
Slammed66
Needs a Big Block
 
Slammed66's Avatar
 
Join Date: Oct 2003
Location: Red Deer , Alberta
Posts: 1,198
Re: Help!!! Brakes apply themselves

The vacuum is into the T in the intake behind the carb.

I just found it!!!!!!

I used an assembled master / booster unit.
I loosened the master from the booster and the brakes released.!!!!!!!!!!!!

So ill adjust that rod in. And all should be well!!!
Posted via Mobile Device
__________________
1964 Short box
On dropmembers and billets
1962 Suburban family cruiser
1972 K10
Slammed66 is offline   Reply With Quote
Old 07-19-2013, 12:09 AM   #4
IntegratedTJ
Registered User
 
IntegratedTJ's Avatar
 
Join Date: Jul 2013
Location: Vallejo, California
Posts: 71
Re: Help!!! Brakes apply themselves

Good deal. Glad you fixed your problem!
IntegratedTJ is offline   Reply With Quote
Old 07-19-2013, 12:16 AM   #5
t korinek
Truckin' Krazy
 
t korinek's Avatar
 
Join Date: May 2000
Location: mesa az
Posts: 6,194
Re: Help!!! Brakes apply themselves

There is a tool made for adjusting that rod to the proper depth, it makes it so you don't have to guess, I have some of them available.
Tom
__________________
Dealer for:
American Auto Wire
Precision weatherstripping
Dakota Digital
Trim parts Carpets
Truck World seat covers
& Many others
Chevy Parts locator in Mesa AZ!
t korinek is offline   Reply With Quote
Old 07-19-2013, 06:53 AM   #6
nightmare
Senior Member
 
nightmare's Avatar
 
Join Date: May 2002
Location: Hammond, WI
Posts: 1,817
Re: Help!!! Brakes apply themselves

Did you also replace the proportioning valve? Drum/drum valves are different from disc/drum valves.
Posted via Mobile Device
__________________
Mike

2001 Dakota R/T - Silver CC - 1 of 1671 •360 w/46RE •392 limited slip
1972 Chevy Suburban - Turquoise/Black
1969 Chevy C/10 - Blue LWB •350 w/ 700R4 •3.73 posi •PS PB A/C - SOLD

Using your turn signal is not "giving information to the enemy"

67-72 FAQ

Quote:
Originally Posted by GMCMAX View Post
My lugnuts require more torque than your honda makes!
nightmare is online now   Reply With Quote
Old 07-19-2013, 02:57 PM   #7
RogerKoop
Senior Member
 
RogerKoop's Avatar
 
Join Date: Nov 2012
Location: Shawnee, KS
Posts: 1,824
Re: Help!!! Brakes apply themselves

I've had this happen in the past. What is happening is the bleed back hole in the master cylinder is plugged or it has pressure on it so it can not bleed back. You may have the rod between the master cylinder and booster to long and will cause this issue.
__________________
Roger Koop
RogerKoop is offline   Reply With Quote
Reply

Bookmarks


Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump


All times are GMT -4. The time now is 08:05 PM.


Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2025, vBulletin Solutions Inc.
Copyright 1997-2022 67-72chevytrucks.com