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Re: Brake Push Rod - 1971 Challenger
[Re: newvcode]
#552373
12/13/09 12:45 PM
12/13/09 12:45 PM
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Joined: Dec 2007
Posts: 18,157
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DAYCLONA
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Ok....if you unbolt the master cylinder, the push rod that sticks out of the booster will have a threaded pushrod, you must measure the depth of the master cylinder's rear bore from it's mounting base, then adjust the length of the threaded pushrod, leaving approx 1/16" clearance, anything more will require the pedal to travel more to engage the brakes, if you make the pushrod too long, it will preload the master causing the brakes to drag, or possibly lock the front,....if you've replaced the master, this service must be performed, as new/rebuilt masters have varying bore depth deminsions when assembled due to machining and parts differences/tolerences
Last edited by DAYCLONA; 12/13/09 12:52 PM.
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Re: Brake Push Rod - 1971 Challenger
[Re: newvcode]
#552375
12/13/09 12:58 PM
12/13/09 12:58 PM
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Joined: Nov 2003
Posts: 36,041
Lincoln Nebraska
RapidRobert
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What Dayclona said. What issue are you having?
live every 24 hour block of time like it's your last day on earth
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Re: Brake Push Rod - 1971 Challenger
[Re: RapidRobert]
#552376
12/13/09 02:07 PM
12/13/09 02:07 PM
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Joined: May 2004
Posts: 847
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Quote:
What Dayclona said. What issue are you having?
Thanks! I changed out the pads on my front discs (original Floating type). To get the new pads to fit, I needed to depress the piston back further than its current, "all the way back position." I have done this many times before on other cars... I took off the top of the Master Cylinder and then used one of the old pads as a platform using a C-Clamp to tighten back the piston. There was resistance, but nothing more than I have experienced before with other cars.
After I got the wheels on, I gave them a spin and they rotated with the appropriate amount of (slight) drag. When I went for a test drive, After a about 5 minutes I lost the pedal... it went to the floor and barely stopped the car... eventually, it would not stop the car !!!!
I got back to the garage and jacked up the front and tried to spin the wheels, they were almost immovable. After some thought about the thickness of the new pads, I put the old ones back on... the wheels spun freely now as well. I went for a test drive and had the same series of issues - the wheels locked up and I lost pedal.
The assumption is, I popped a seal internally in the MC, although there are no leaks of any kind. Could this be due to a rod adjustment that had the pedal fairly low to begin with? I am at a loss.
I wanted to see if I could "adjust a fix" before rebuilding the MC which appears to be bad, but may not be.
Thanks
Ritchie
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Re: Brake Push Rod - 1971 Challenger
[Re: newvcode]
#552377
12/13/09 04:59 PM
12/13/09 04:59 PM
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Joined: Nov 2003
Posts: 36,041
Lincoln Nebraska
RapidRobert
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Everything was good ex the pedal when applied was a bit low and you just R&R'd the pads cause they were getting thin? I'm thinking the prob is at the calipers/pads (pistons binding or pads hanging up). Might jack up & pull one or both front wheels then idle it & pump it & get the front wheels locked/binding & see if anything jumps out at you & if not crack the (disc) line at the M/C & see if that releases it.
live every 24 hour block of time like it's your last day on earth
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Re: Brake Push Rod - 1971 Challenger
[Re: RapidRobert]
#552378
12/13/09 09:41 PM
12/13/09 09:41 PM
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Joined: May 2004
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Quote:
if not crack the (disc) line at the M/C & see if that releases it
Wouldn't bleeding accomplish the same thing? I ask, because I have bled out the lines a bit and it changed nothing. I also assume that if there was some undue pressure caused by whatever.... when I opened the bleeders the fluid would scream out - which it did not do.
Thanks for the help guys...
Ritchie
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Re: Brake Push Rod - 1971 Challenger
[Re: newvcode]
#552381
12/13/09 10:52 PM
12/13/09 10:52 PM
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Joined: Nov 2003
Posts: 36,041
Lincoln Nebraska
RapidRobert
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If you reread my post "excessive psi" was my second choice after caliper/pads mechanically hanging up. (also possibly the square seal(s)) but I wouldn't think both sides would have malfunctioned from the pistons being compressed.
live every 24 hour block of time like it's your last day on earth
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Re: Brake Push Rod - 1971 Challenger
[Re: RapidRobert]
#552382
12/13/09 11:46 PM
12/13/09 11:46 PM
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Joined: Feb 2003
Posts: 10,218
Someplace you aren't
SomeCarGuy
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I have had pad replacement cause the caliper to seize up.
When you push the piston back, it lodges in the bore, likely a ridge in the. Could have gotten cocked at an angle.
Is this both front wheel locked or tight or just one?
Doesn't sound like you pressure bled the brakes. Sounds from your post that you just gravity bled, which can be OK but I have found that pressure bleeding gets more air out, at least quicker than gravity bleeding repeatedly. Get a helper or one of the one man kits that cost about 10 bucks or so.
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Re: Brake Push Rod - 1971 Challenger
[Re: SomeCarGuy]
#552383
12/14/09 12:59 PM
12/14/09 12:59 PM
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Joined: May 2004
Posts: 847
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Quote:
When you push the piston back, it lodges in the bore, likely a ridge in the. Could have gotten cocked at an angle.
Both. But, it's possible, unlikely, but possible, that I cocked them both. How did you "square" them back up?
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Re: Brake Push Rod - 1971 Challenger
[Re: newvcode]
#552384
12/14/09 02:07 PM
12/14/09 02:07 PM
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Joined: Nov 2003
Posts: 36,041
Lincoln Nebraska
RapidRobert
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The seal & boot kits are cheap ($2.99 at advance auto) or rebuilt calipers are cheap also.
live every 24 hour block of time like it's your last day on earth
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Re: Brake Push Rod - 1971 Challenger
[Re: RapidRobert]
#552385
12/14/09 02:56 PM
12/14/09 02:56 PM
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Joined: May 2004
Posts: 847
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Quote:
rebuilt calipers are cheap also.
Great thought, any preferred vendor? NAPA has them for < 40 each side. YO has them for > $100 each :-)
I really appreciate your help on this!!!!!
Ritchie
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Re: Brake Push Rod - 1971 Challenger
[Re: RapidRobert]
#552387
12/14/09 07:51 PM
12/14/09 07:51 PM
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Joined: May 2004
Posts: 847
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Quote:
I was not happy with my slightly caustic reply
No worries... I really appreciate the help and will keep you posted on the progress.
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Re: Brake Push Rod - 1971 Challenger
[Re: newvcode]
#552388
12/14/09 08:10 PM
12/14/09 08:10 PM
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Joined: Nov 2003
Posts: 36,041
Lincoln Nebraska
RapidRobert
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the 1st parts guy (A newbie) told me that the 71 chally and 73 dart calipers had the same # but I knew something wasn't right then it hit me that 73 up A body discs are sliders(I'm using them) and you have floaters. SO I called back just now & another guy rechecked & they are different (& therefore different #'s). The bore difference info is good as the 76 A and all F body calipers are the larger 2.75" bore dia & I used them (76 A slider calipers) on my 65 dart (74 A disc spindles).
live every 24 hour block of time like it's your last day on earth
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Re: Brake Push Rod - 1971 Challenger
[Re: newvcode]
#552389
12/15/09 12:38 AM
12/15/09 12:38 AM
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Joined: Feb 2003
Posts: 10,218
Someplace you aren't
SomeCarGuy
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Quote:
Quote:
When you push the piston back, it lodges in the bore, likely a ridge in the. Could have gotten cocked at an angle.
Both. But, it's possible, unlikely, but possible, that I cocked them both. How did you "square" them back up?
To be clear, the piston would get cocked on the way back out when it catches that ridge. Then it is just plain hung up. Really nothing short of a hone job will fix it.
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