Lost brakes, almost crashed the Cord!

[Frank DuVal]

4 hours ago, Cadillac Fan said:

but after having a similar event in a single circuit break system, I converted to a dual circuit master cylinder.  

Every through the red light brake failure I had was on a dual circuit master cylinder brake system! 😲

 

I test my single circuit systems in the driveway frequently, see hard HARDER test above, but take the dual system for granted on daily drivers. I'm changing this attitude!

[46 woodie]

It's not as simple of just adding a dual master cylinder. If that's the way you are going, I would call some companies that do custom brake systems. I'm assuming you want to stay with your stock drum brakes. If that is your intent then there are several way's that a dual master can be used. All involve a combination valve and other components such as a metering valve and residual valves. If you're happy with the way the car stops now, I would just change the bad hose and enjoy the car.

[Frank DuVal]

Drum brakes standard on most domestic cars until 1970/71. Dual circuit systems mandated in 1967, several companies made them before then. So there are common dual pot master cylinders that were designed for 4 drum systems. Being all 4 drums there is no proportioning valve needed. Sure, there is that switch block after the master cylinder, but that is only a switch to light the red light on the dash saying one brake system has no/reduced pressure. This comes up a lot on discussion forums, and no, it is NOT a proportioning valve, just a differential pressure switch. No combination valve! No metering valves. System will brake fine without it, just the red light will not come on when there is trouble. Not that the red light on the dash is the first indication of brake failure. driver sweating is! Who looks at the dash during a brake failure event? You look for a way out!😲

 

Yes there are residual valves, just like in the single pot system for drum brakes. Usually internal to the master, sometimes on the output fittings. This is what the return springs on the shoes do, pull back against the residual pressure of the system.

 

[60FlatTop]

Just because something appears to work doesn't mean it is designed correctly. I see a lot of dual master cylinders installed for reasons I generally don't agree with and they appear to stop the car.

On a retrofit the dual master cylinder may have 3/16" or metric fittings smaller than the original. Does one reduce the pipe at the master cylinder or a junction block. Or at the wheel cylinders? And how was the decision made? I know there are varied volumetric displacements in the system chambers. Is the new system calculated accordingly? I have never seen anything on it.

 

On the Cord that fitting at the bulkhead connection looks like a refrigeration flare nut. Did ACD use those fittings? The exposed pipe at that point looks to be 1/4". Is there a similar arrangement of fittings going out to the front brakes?

 

You have to be really careful of things that were passed on from the generation famous for quotes like "We have done so much with so little for so long we can now do anything with nothing". Could there be an instance of light fingers in the refrigeration shop?

 

I remember an afternoon of being upside down in the alligator engine compartment of a Packard sweating to dehydration installing the correct bracket and generator. All the time thinking how proud the previous person had been on his ingenuity.

 

Verify the existing system parts and condition. Returning it to original and maintaining it will give you the best satisfaction. And avoid some guy sitting at the dinner table 23 years from now trying to catch his breath to tell his wife what he did that day.