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Replacing a single Master Cylinder #2698808
09/18/19 10:25 PM
09/18/19 10:25 PM
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Sammy Offline OP
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I'm replacing a single master cylinder and was wondering after I successfully bench bled the new master cylinder, after I remove the old leaking MC, and put on the new single master cylinder with just 1 line, will the brakes need to be rebled or can I get away with just the simple swap out and have a normal brake pedal?

Re: Replacing a single Master Cylinder [Re: Sammy] #2698811
09/18/19 10:45 PM
09/18/19 10:45 PM
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Sniper Offline
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I am sure someone will say they did that. I never got that lucky and I wouldn't plan on it even if I did.

Re: Replacing a single Master Cylinder [Re: Sniper] #2698848
09/19/19 01:20 AM
09/19/19 01:20 AM
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John Brown Offline
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Whenever I did that kind of thing, I would lightly pump the brake pedal tiny strokes over and over again until the bubbles quit coming up in the reservoir. Nine times out of ten, it was fine doing it that way.


July 19th should be "Drive Like Rockford Day". R.I.P. Jimmie.
Re: Replacing a single Master Cylinder [Re: John Brown] #2698863
09/19/19 06:57 AM
09/19/19 06:57 AM
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Sammy Offline OP
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Originally Posted by John Brown
Whenever I did that kind of thing, I would lightly pump the brake pedal tiny strokes over and over again until the bubbles quit coming up in the reservoir. Nine times out of ten, it was fine doing it that way.



I got out all the bubbles bench bleeding the new master cylinder.
Just want to pop out the old one and put in the new one without having to start bleeding the drums.
Can it just work with just the bench bleed?

Re: Replacing a single Master Cylinder [Re: Sammy] #2698896
09/19/19 09:15 AM
09/19/19 09:15 AM
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South Bend
John Brown Offline
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What difference is there whether the master cylinder clamped in a vise or bolted on a vehicle? Answer, NONE. As long as you get the air out, you're good. I flat rated for a few years and as long as the m-cylinder was level on the car or truck, I bench bled them on the vehicle. I did crack the line fitting at the last moment to keep any air from getting into the brake lines. I always felt that as long as the original brake lines were still full of fluid, there was no air gonna jump in there, so no need to bleed them out. You may want to rebleed the lines, but that is your choice, and not a necessity.


July 19th should be "Drive Like Rockford Day". R.I.P. Jimmie.
Re: Replacing a single Master Cylinder [Re: John Brown] #2698921
09/19/19 10:05 AM
09/19/19 10:05 AM
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Sammy Offline OP
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Originally Posted by John Brown
What difference is there whether the master cylinder clamped in a vise or bolted on a vehicle? Answer, NONE. As long as you get the air out, you're good. I flat rated for a few years and as long as the m-cylinder was level on the car or truck, I bench bled them on the vehicle. I did crack the line fitting at the last moment to keep any air from getting into the brake lines. I always felt that as long as the original brake lines were still full of fluid, there was no air gonna jump in there, so no need to bleed them out. You may want to rebleed the lines, but that is your choice, and not a necessity.


Going to swap out the MC in a few minutes.
Will report back.
Will put a cinder block on the pedal and crack the single line to make sure no air is in the line and MC fitting.

Re: Replacing a single Master Cylinder [Re: Sammy] #2698987
09/19/19 02:26 PM
09/19/19 02:26 PM
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Sniper Offline
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And one wonders why I let no one else touch my vehicles.

One of the things bleeding your brakes does aside from making sure there is no air in the system is flush all that old fluid out. You are supposed to do that yearly with DOT3 type stuff.

Re: Replacing a single Master Cylinder [Re: Sammy] #2698994
09/19/19 03:09 PM
09/19/19 03:09 PM
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UPPER MICHIGAN, MARQUETTE COUN...
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Originally Posted by Sammy
I'm replacing a single master cylinder and was wondering after I successfully bench bled the new master cylinder, after I remove the old leaking MC, and put on the new single master cylinder with just 1 line, will the brakes need to be rebled or can I get away with just the simple swap out and have a normal brake pedal?


Normally that will work. However with a leaking master if it was ever ran low on fluid you may have air already trapped in the system. If possible bleed the rest of the system. Most re builders specify not to mix fluids or old fluids that could void the cylinders warranty.

Re: Replacing a single Master Cylinder [Re: NITROUSN] #2699033
09/19/19 05:45 PM
09/19/19 05:45 PM
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Sammy Offline OP
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Originally Posted by NITROUSN
Originally Posted by Sammy
I'm replacing a single master cylinder and was wondering after I successfully bench bled the new master cylinder, after I remove the old leaking MC, and put on the new single master cylinder with just 1 line, will the brakes need to be rebled or can I get away with just the simple swap out and have a normal brake pedal?


Normally that will work. However with a leaking master if it was ever ran low on fluid you may have air already trapped in the system. If possible bleed the rest of the system. Most re builders specify not to mix fluids or old fluids that could void the cylinders warranty.


Well the new aftermarket Master Cylinder is metric tapped and I cant get a pedal.
Took off new one and cleaned up the old one.
Is there a way to get those 2 bolts holding the piston in easy?
Putting this thing back together is a real pain.
Had to take a break.

Re: Replacing a single Master Cylinder [Re: Sammy] #2699179
09/20/19 10:24 AM
09/20/19 10:24 AM
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moparx Offline
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why in the world would a replacement single bowl master be tapped with metric threads ?
beer

Re: Replacing a single Master Cylinder [Re: moparx] #2699182
09/20/19 10:33 AM
09/20/19 10:33 AM
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Sammy Offline OP
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Originally Posted by moparx
why in the world would a replacement single bowl master be tapped with metric threads ?
beer



No clue.

Re: Replacing a single Master Cylinder [Re: Sammy] #2699187
09/20/19 10:53 AM
09/20/19 10:53 AM
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north of coder
moparx Offline
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the great world of replacement parts we live in....... down
was this a "brand name" chain store part, or a restoration shop item ?
beer

Re: Replacing a single Master Cylinder [Re: moparx] #2699231
09/20/19 01:25 PM
09/20/19 01:25 PM
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Sammy Offline OP
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Originally Posted by moparx
the great world of replacement parts we live in....... down
was this a "brand name" chain store part, or a restoration shop item ?
beer



Ebay part....
Couldnt find a OE single master cylinder anywhere else.
This part is junk.

Re: Replacing a single Master Cylinder [Re: Sammy] #2699287
09/20/19 04:37 PM
09/20/19 04:37 PM
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Originally Posted by Sammy
Originally Posted by moparx
the great world of replacement parts we live in....... down
was this a "brand name" chain store part, or a restoration shop item ?
beer



Ebay part....
Couldnt find a OE single master cylinder anywhere else.
This part is junk.

Sometimes you get what you pay for, sometimes you get hammer whineyshruggy


Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)
Re: Replacing a single Master Cylinder [Re: Cab_Burge] #2699717
09/22/19 07:36 AM
09/22/19 07:36 AM
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Sammy Offline OP
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To put the master cylinder back in, should I remove the rod off the brake pedal and assemble the master cylinder as one unit and then reattach the rod back ?
Or leave the rod in place?

Re: Replacing a single Master Cylinder [Re: Sammy] #2699786
09/22/19 10:59 AM
09/22/19 10:59 AM
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moparx Offline
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i guess it would depend on how hard the rod [with the rubber retainer ring] pushes into the receiver groove in the master's piston.
sometimes they can be a bear, and in those cases, i leave the rod attached to the pedal.
this way, you can use your leg power to push it into position. this method requires either a helper to guide the rod into position while the master is attached to the firewall, or leave the rod off the pedal and insert into the piston bore after the master is attached to the firewall, then bolt to the pedal.
if the rod can be inserted fully into the master's piston while being bench bled, that is usually the best method.
i have done it both ways.
remember to slightly lube the retainer ring to make it a tad easier to insert the rod into the master.
beer







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