BRAKE ISSUE / PART 2 ?
#1661945
08/21/14 01:44 PM
08/21/14 01:44 PM
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Joined: Jan 2003
Posts: 10,647
S.E.Ohio
Magnumguy
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I Live Here
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OP
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S.E.Ohio
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Some time back, I repurchases a low mileage 78 Magnum (long story).
Previous owner had issues w/the calipers locking up, so figuring that the calipers were aged and had the original phenolic? pistons, they'd need changed. So... I changed the calipers, hydraulic lines, and pads. Road testing and they keep not releasing, last trip out and it did so again. I did have a hard time bleeding these for some reason. Now, that they're bled they're sticking or hanging up. I re-inspected the calipers and appear to be free moving.
Would the master cylinder cause this or should I remove/replace the proportioning valve? Oh, the rears work just fine BTW.
Thoughts
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Re: BRAKE ISSUE / PART 2 ?
[Re: Magnumguy]
#1661946
08/21/14 02:15 PM
08/21/14 02:15 PM
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Joined: Nov 2003
Posts: 36,041
Lincoln Nebraska
RapidRobert
Circle Track
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Circle Track
Joined: Nov 2003
Posts: 36,041
Lincoln Nebraska
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booster pushrod round nub clearance to bottom of MC rear piston "thimble" correct (~.020" or so). EDIT you could unbolt the MC and pull it forward a bit & insert some spacers between MC and booster to space it forward then bolt it back snug & that'll quickly tell you if the pushrod was preloading the piston. Not sure how far to space it, I'd wing it & see how it goes
Last edited by RapidRobert; 08/22/14 10:20 PM.
live every 24 hour block of time like it's your last day on earth
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Re: BRAKE ISSUE / PART 2 ?
[Re: RapidRobert]
#1661947
08/23/14 12:38 AM
08/23/14 12:38 AM
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Joined: Sep 2003
Posts: 1,688
Marlboro, NY, USA
Rick_Ehrenberg
top fuel
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top fuel
Joined: Sep 2003
Posts: 1,688
Marlboro, NY, USA
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Quote:
booster pushrod round nub clearance to bottom of MC rear piston "thimble" correct (~.020" or so). EDIT you could unbolt the MC and pull it forward a bit & insert some spacers between MC and booster to space it forward then bolt it back snug & that'll quickly tell you if the pushrod was preloading the piston. Not sure how far to space it, I'd wing it & see how it goes
Bingo! If you open a bleeder screw and the drag goes away instantly, that's confirmation.
Rick
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Re: BRAKE ISSUE / PART 2 ?
[Re: Rick_Ehrenberg]
#1661948
08/23/14 11:01 PM
08/23/14 11:01 PM
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Joined: Nov 2003
Posts: 36,041
Lincoln Nebraska
RapidRobert
Circle Track
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Circle Track
Joined: Nov 2003
Posts: 36,041
Lincoln Nebraska
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Rick has you covered even better. With the wheels off the ground, crack a bleeder & you'll know in 5 seconds if it is a (psi) problem (if the wheels go free(er). discs always have some drag some calipers more than others
live every 24 hour block of time like it's your last day on earth
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Re: BRAKE ISSUE / PART 2 ?
[Re: nomore65BelvJim]
#1661950
08/23/14 11:57 PM
08/23/14 11:57 PM
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Joined: Jan 2003
Posts: 10,647
S.E.Ohio
Magnumguy
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I Live Here
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OP
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S.E.Ohio
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Quote:
Does it have the correct master?
It's original one, yes.
Now, can that piston or rod be adjusted? Or do like one poster said put in spacers?
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Re: BRAKE ISSUE / PART 2 ?
[Re: Magnumguy]
#1661952
08/24/14 10:27 AM
08/24/14 10:27 AM
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Joined: Sep 2003
Posts: 19,591
north of coder
moparx
"Butt Crack Bob"
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"Butt Crack Bob"
Joined: Sep 2003
Posts: 19,591
north of coder
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Quote:
Quote:
Does it have the correct master?
It's original one, yes.
Now, can that piston or rod be adjusted? Or do like one poster said put in spacers?
bill, that nub on the booster rod is threaded. no spacers are needed on the master to booster connection.
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Re: BRAKE ISSUE / PART 2 ?
[Re: zrxkawboy]
#1661954
08/24/14 12:14 PM
08/24/14 12:14 PM
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Joined: Nov 2003
Posts: 36,041
Lincoln Nebraska
RapidRobert
Circle Track
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Circle Track
Joined: Nov 2003
Posts: 36,041
Lincoln Nebraska
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If PB, the round threaded nub on the end of the booster pushrod yes it is adjustable. Spacing the MC forward was only a quick check to see if the threaded nub is too long & is in fact preloading the piston & is causing the problem. If it is then seperate the MC & thread in (shorten) the nub. If MB the adjustable manual brake pushrod in the pic is for restoring proper brake pedal height, the MC piston return springs in a MB app will always return the pedal past the preload problem area
live every 24 hour block of time like it's your last day on earth
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Re: BRAKE ISSUE / PART 2 ?
[Re: RapidRobert]
#1661955
08/25/14 01:22 PM
08/25/14 01:22 PM
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Joined: Jan 2003
Posts: 10,647
S.E.Ohio
Magnumguy
OP
I Live Here
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OP
I Live Here
Joined: Jan 2003
Posts: 10,647
S.E.Ohio
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Thanks y'all! I bought a new MC ($26 @ NAPA), didn't get to install it yet.  Life does get in the way. HOpe to get it in tonight and we'll see what's up
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