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Need help with master cylinder!

prgjr1

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hi all, I have a 70 challenger 340 with power disc brakes. Is the correct master cylinder the one with the flush piston and holding tab or the one with the protruding piston and no tab. Problem is there is a new master installed and it leaks from the back and down the front of the booster. Not sure what's going on or how to fix it. Thanks
 

Xcudame

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The original part number for the 70 master cylinder with power disc brakes is 2944453 casting number 2239171.

And yes, the current master cylinder need rebuilt or replaced with the above part number.
 

Steve340

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I have two cars with the double diaphragm "Hemi" style booster and they have the protruding piston.
I think if you have the pancake Midland Ross booster it has the flush piston.
It was a few years ago - Pretty sure this is correct.
You need to make sure the booster pushrod clearance is right in any case.

Is the master lid leaking?
If not as Chryco said a new cylinder.
 

prgjr1

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I have two cars with the double diaphragm "Hemi" style booster and they have the protruding piston.
I think if you have the pancake Midland Ross booster it has the flush piston.
It was a few years ago - Pretty sure this is correct.
You need to make sure the booster pushrod clearance is right in any case.

Is the master lid leaking?
If not as Chryco said a new cylinder.
I have the flush mount piston with the tear drop holding tab. I beleive it is incorrect and need the one with the protruding piston. This is what I need help with, which is the correct master for my car ? Thanks

20231115_130300.jpg


Screenshot_20231115-170320_eBay.jpg
 

prgjr1

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Notice the spacer , is that specific to the master or the booster for my car is it needed only for certain masters ? Also, both reservoirs are the same size and I know they should be 1 smaller then the other.

20231115_130929.jpg


20231115_130630.jpg
 

Xcudame

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Your correct master cylinder should look something like this. Don't mind the dust and grime, it's got over 100,000 miles on it!

IMG_20231116_151638487.jpg
 

moparleo

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You have a drum brake Master Cylinder.
The part that you are calling a spacer is acting as a spacer/washer to take up the space of the M/C piston retaing clip. Without it the master Cylinder would not evenly tighten up to the booster.
Always buy new when you can. Not all rebuilts are trustworthy.
Click on this link for one option.
1966-1974 Mopar Bendix Master Cylinder, 1.125 Inch Bore
 
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prgjr1

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Should I remove the spacer when I put on the correct master ?
 

prgjr1

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You have a drum brake Master Cylinder.
The part that you are calling a spacer is acting as a spacer/washer to take up the space of the M/C piston retaing clip. Without it the master Cylinder would not evenly tighten up to the booster.
Always buy new when you can. Not all rebuilts are trustworthy.
Click on this link for one option.
1966-1974 Mopar Bendix Master Cylinder, 1.125 Inch Bore
Should I remove that spacer and mount the correct master to the booster without it. I believe the correct master has the slightly protruding plunger
 

Xcudame

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Yes, remove the spacer and turn in the plunger poking out of the vacuum booster in the same thickness. If the plunger engages the new master cylinder too much, it will mess it up!
 

prgjr1

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Is this the correct master 70 challenger power disc with protruding plunger ? Thanks

Screenshot_20231115-170320_eBay.jpg
 

Xcudame

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340challconvert

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Here is a pic of my original pb booster (early Oct. 70 340 Challenger w Disc brakes) face of yours is a little different then mine and my original correct master cylinder (2229171) for disc brakes (thermometer front) with the stop on the plunger. There is a inexpensive tool to correctly set the plunger depth coming from the booster

brake master back original.jpg


Brake Booster dino 4.jpg


master brake w booster.jpg


tool.jpg
 

prgjr1

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Here is a pic of my original pb booster (early Oct. 70 340 Challenger w Disc brakes) face of yours is a little different then mine and my original correct master cylinder (2229171) for disc brakes (thermometer front) with the stop on the plunger. There is a inexpensive tool to correctly set the plunger depth coming from the booster

View attachment 115193

View attachment 115194

View attachment 115195

View attachment 115196
When I look up the masters for my car they all show the plunger sticking out slightly not the ones with the tab so this is where I'm confused the pic I posted shows the one I have been seeing listed for my car.. crazy
 

prgjr1

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When I look up the masters for my car they all show the plunger sticking out slightly not the ones with the tab so this is where I'm confused the pic I posted shows the one I have been seeing listed for my car.. crazy
And the one with the tab thats flush is on my car but it was replaced so it may be wrong. Also has a spacer for the tab. I have a pic posted for that . I don't want to get the wrong one.driving me nuts lol
 

Steve340

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It is kind of likely you have a drum brake power booster - I do not know if they are different.
In any case if the master bolts up properly it will work.
I would buy the one the one with the protruding piston.
You might still need the spacer - but see how it fits without it.
Buy the tool posted by 340challconvert - it takes all the guesswork out of setting the booster pushrod clearance.
Take care not to lose the booster reaction pad. It is a hard rubber pad between the booster diaphragm and the pushrod.
 

prgjr1

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When I look up the masters for my car they all show the plunger sticking out slightly not the ones with the tab so this is where I'm confused the pic I posted shows the one I have been seeing listed for my car.. crazy
do you know where I can get that tool ?
 
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