Master Cylinder Jerry-Rigged???

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soonercruiser

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Now I think I have seen it all!
As I have posted several times, the previous owner (and son) of my 67 Barracuda Jerry-rigged a lot of stuff that I have had to correct.

Since I went to Wilwood front disc brakes, I had been delaying upgrading the master cylinder from the drum brake master.
So today, we take off the master cylinder, and THIS is what we see!!!!! :eek:

old master patch.jpg


I dont think that extra plate and screws are supposed to be there.
My best guess is, with all the heavy grease around the rod, the piston cups were bad, and this was their attempt to stop a fluid leak.
I have ordered the matching master cylinder repair kit.
 
Not jerry rigged. That's simply how the master cylinder pushrod is retained. They aren't all like that, but some are. Nothin unusual.
 
There is usually a retainer that has the keeper for the dust bellows.

Screenshot_20250128-193233.png


Screenshot_20250128-193259.png


Newer master cylinders use a snap ring and do not have the 2 mounting holes.
 
But, if the push rod is in-place, and the master cylinder is mounted/install on the firewall, is that even necessary???
Yeah. How is it gonna get bolted on without the guts of the master cylinder shooting the pushrod out and pukin the master cylinder guts all over the floor? There are two pretty stout springs inside the master cylinder. I can tell you've never had one apart.
 
---------Or UNbolted and removed long after the mech/ owner has FORGOTTEN that the retainer "isn't there" LOL
 
OK! I have been searching the web and my service manual for anything that looks remotely like the picture I posted of my old master cylinder piston area.
The following image is the only one I have run across, and is from the service manual.
And the screw and tab only seems to be there for retaining the piston barrel.
None of all the other pictures and diagrams that I have found have anything retaining the piston.
So, I am going to assume that is what the plate and screws were for on my old master cylinder picture.

piston retaining screw.jpg


So, the question in my minds is....(as RustRatRod said).....
With both a new master cylinder, and new push rod kit, do I even need such a thing since it's not an "always"???
I have also ordered a MOPAR gasket for the MC.
 
wtf? there is no "piston barrel" it's just the piston. that's it.

master is machined, piston is close tolerance fit, seals do the rest. springs handle the action inside.

yes you need retainer. it's the belt and suspenders fail safe along with the rod, rod retaining grommet thingy and pedal stop (or in some cases the brake switch).
 
The piston retainer is for shipping only. The retainer with the integrated dust bellows gets put on by the installer.

With out the retainer the piston WOULKD come out of the MC. The brake pedal can move toward the rear of the car if you lift up so on it. The retainer or an internal snap ring is the only thing to prevent the rearmost piston from coming out.
 
OK! I have been searching the web and my service manual for anything that looks remotely like the picture I posted of my old master cylinder piston area.
The following image is the only one I have run across, and is from the service manual.
And the screw and tab only seems to be there for retaining the piston barrel.
None of all the other pictures and diagrams that I have found have anything retaining the piston.
So, I am going to assume that is what the plate and screws were for on my old master cylinder picture.

View attachment 1716359284

So, the question in my minds is....(as RustRatRod said).....
With both a new master cylinder, and new push rod kit, do I even need such a thing since it's not an "always"???
I have also ordered a MOPAR gasket for the MC.
That's what I've told you all along. The metal strap and screws retain not only the pushrod, but the whole guts of the master cylinder. LEAVE IT IN PLACE. Because of manufacturing variances by different companies, you may find something OTHER than a tab or strap retaining the master cylinder guts, like a snap ring. The factory service manual is a poor judge OF THAT, since these cars are SO OLD the master cylinders may have been replaced more than a few times, so who knows exactly what you will find?
 
OK! I have been searching the web and my service manual for anything that looks remotely like the picture I posted of my old master cylinder piston area
I'm guessing the biggest issue you are having is finding a compatible master cyl that looks the same


This master cyl is the newer style with the snap ring that retains the piston


1738196032423.png





This is a modern day rebuilt or new master cyl that has the threaded holes for the external keeper.

1738196174102.png


They are functionally the same!

EXCEPT for how the dust bellows mounts.


This is how the bolt on retainer / dust bellows mount bolts on. it might use bolts as shown or flathead screws

1738196470592.png




This is what the gasket style dust bellows mount looks like for the newer snap ring retained master cyl. This is sandwiched between the MC and the firewall
1738196767119.png
 
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