Master Cylinder Upgrade

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6pk2goDemon

6pk2goDemon

Mopar Mod
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I've been researching this brake upgrade here on FABO for awhile.

Replaced the MC on my Demon today from this 1 1/32" bore which was not leaking & still working....


P1030323.JPG


To this 15/16" bore....

P1030327.JPG


It made a significant difference in pedal pressure needed to stop the car & thought it was worth mentioning :D


P1030330.JPG
 
What's the new master out of? I'd like to be able to tell the guy at O'Reilly otherwise it'll be a complete circus.
 
Very nice. I did something similar (although completely by mistake) when I replaced the M/C on my Ford truck. When I researched it, I discovered someone had actually replaced the original M/C with an incorrect model. When I replaced it, I made SURE to get one for the exact application and it made a big difference. Small details like that can make s big difference.
 
Looks like you had drum brakes? ( seeing the old master cylinder) The master you replaced it with is for disc brakes up front. It will work......but not correct Drum brakes and unknown for safety. Drum brakes always had even sized fluid reservoirs...Disc had to different size reservoirs.
You may want to look into this.
 
I used the same one and it leaked in the back and ruined the fresh paint on my firewall. I'm switching to the aluminum 2 bolt when it gets back from the body shop. They seem to be less leak prone.
 
marksmopar1 said:
Looks like you had drum brakes? ( seeing the old master cylinder) The master you replaced it with is for disc brakes up front. It will work......but not correct Drum brakes and unknown for safety. Drum brakes always had even sized fluid reservoirs...Disc had to different size reservoirs.
You may want to look into this.
Click to expand...
The larger reservoir is for front disc brakes. It'll work with drums. But... now there is no residual pressure valve on the front brake system, because a m/c made for disc brakes does not have one. I'm not sure if this is going to cause problems or not.
 
turtleheadjoe said:
What's the new master out of? I'd like to be able to tell the guy at O'Reilly otherwise it'll be a complete circus.
Click to expand...

The application for the new one is 73-76 A-Body disc brake cars Raybestos #36406, but I couldn't find any suppliers here that sold that brand....

So I had to dig some more :BangHead:
 
RustyRatRod said:
Very nice. I did something similar (although completely by mistake) when I replaced the M/C on my Ford truck. When I researched it, I discovered someone had actually replaced the original M/C with an incorrect model. When I replaced it, I made SURE to get one for the exact application and it made a big difference. Small details like that can make s big difference.
Click to expand...

Yep, research was the key for me too!! Thanks Rob :)
 
marksmopar1 said:
Looks like you had drum brakes? ( seeing the old master cylinder) The master you replaced it with is for disc brakes up front. It will work......but not correct Drum brakes and unknown for safety. Drum brakes always had even sized fluid reservoirs...Disc had to different size reservoirs.
You may want to look into this.
Click to expand...

No, it's a factory disc brake car. The equal reservoir MC had me confused a bit too, but research has proved it to be correct from Ma Mopar...

Never say never :)
 
Sedanman said:
I used the same one and it leaked in the back and ruined the fresh paint on my firewall. I'm switching to the aluminum 2 bolt when it gets back from the body shop. They seem to be less leak prone.
Click to expand...

Ugh....I hope it doesn't leak!!! I changed out a perfect working one to get a better pedal....
 
69_340_GTS said:
The larger reservoir is for front disc brakes. It'll work with drums. But... now there is no residual pressure valve on the front brake system, because a m/c made for disc brakes does not have one. I'm not sure if this is going to cause problems or not.
Click to expand...

I've always thought the same about disc brake cars. Big & little reservoirs---unequal sized. I was pretty sure this equal reservoir MC was original to my car. 72K miles and KH from the factory....

Here's an old thread for reference...

What is the correct master cylinder for manual disc
 
That's not true at all.
6pk2goDemon said:
No, factory disc brake car. The equal reservoir MC had me confused a bit too, but research has proved it to be correct from Ma Mopar...

Never say never :)
Click to expand...

That's correct. Almost all modern vehicles now have a common reservoir. It's not necessary to have a split reservoir, since the master cylinder itself is split into two distinctly different cylinders and pistons inside. Just look at any modern vehicle with a plastic reservoir. It is not split into different sections at all. That action takes place in the master cylinder body.
 
That master was trouble free for about a year and I was digging around under the hood one day and noticed the paint bubbled from the master down.
 
The pressure varies inversely as bore diameter squared, so dropping from 1-1/32"D to 15/16"D makes a noticeable difference. I use a 7/8"D bore aluminum MC from a 95-99 Breeze on a 2-4 bolt adapter plate (ebay). I don't like the heavy rust-prone cast-iron ones and the plastic reservoirs seal much better. Many people here find the steel lids drip fluid, usually because they have air in the system which makes a geyser as the pedal returns, but any drips indicate a poor seal which can also let moisture in which glycol fluid loves to suck up and cause rust. Not a problem for me because I use silicone fluid. Newer MC's also have a low-level warning switch which you can wire to light the dash lamp - parallel w/ e-brake switch so if either shorts to gnd, the lamp lights. But don't get an MC w/ "bubble flare" ports (~2000+) and use one w/ only 2 ports (for ABS).
 
6pk2goDemon said:
The application for the new one is 73-76 A-Body disc brake cars Raybestos #36406, but I couldn't find any suppliers here that sold that brand....

So I had to dig some more :BangHead:
Click to expand...

Will that also work on the old Kelsey Hayes disc brake cars???
 
Sedanman said:
That master was trouble free for about a year and I was digging around under the hood one day and noticed the paint bubbled from the master down.
Click to expand...

Was your MC new or rebuilt? If this thing starts leaking, I'll be :mad:


RustyRatRod said:
Hell yeah! Glad to see you're an O'Reilly gal!
Click to expand...

We have a store manager that takes great care of us & always goes the extra mile! Since this is their "house brand", I'm guessing it's a Cardone or ??
 
6pk2goDemon said:
Was your MC new or rebuilt? If this thing starts leaking, I'll be :mad:




We have a store manager that takes great care of us & always goes the extra mile! Since this is their "house brand", I'm guessing it's a Cardone or ??
Click to expand...

My understanding it is both Cardone and or Wagner. We've gotten them boxed as BrakeBest, Cardone and Wagner all three. Similar to the Microguard filters. They are rebranded WIX and the O'Reilly brand oil is rebranded Havoline. I use the Microguard filter and O'Reilly brand oil in Kitty's Escape. Not a thing wrong with it.
 
krazykuda said:
Will that also work on the old Kelsey Hayes disc brake cars???
Click to expand...

I would think it would work well on the KH cars. The great thing is it's a direct bolt in/match for the existing brake lines :D We didn't need to change the pushrod either....

Very simple upgrade made a world of difference IMO
 
krazykuda said:
Will that also work on the old Kelsey Hayes disc brake cars???
Click to expand...

Of course it will. There is zero proportioning action in the master cylinder. All of that is handled in the proportioning valve itself, so which master cylinder is there is pretty much a moot point.
 
I've had 2 reman m/c like the OP posted leak out the back in less than a year.

That's one reason I am in the process of switching to DOT5.

The other is that I just painted my engine compartment.

Hope you have better luck.
 
BillGrissom said:
I don't like the heavy rust-prone cast-iron ones and the plastic reservoirs seal much better. Many people here find the steel lids drip fluid, usually because they have air in the system which makes a geyser as the pedal returns, but any drips indicate a poor seal which can also let moisture in which glycol fluid loves to suck up and cause rust.
Click to expand...

I painted the reservoir with Krylon Clear. It should hold up in our dry climate as long as it doesn't leak. Here's my homemade painting jig LOL

P1030342.JPG
 
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