The Stovebolt Site Forums The Shop Area Driveline Brake Proportioning Valve Failure

A few years ago I installed a CPP front disc brake conversion kit on my 56 3100. Last week I suddenly began losing pedal; I thought I had a bad wheel cylinder on the rear. Long story short, the provided proportioning / combination valve had sprung a colossal leak. The fitting in which the rear brake line goes had an orifice with a small rubber plug in it held in place by a pressed in star washer. The fitting on the replacement valve i ordered is solid and doesn’t have this orifice (although replacement valves with the orifice are available).

Does anyone know what is the function of this orifice and what does it mean when it sees enough pressure to rupture the plug or push it out? I already attended Google-U and learned nothing.

Thx!
Greg

Greg I wish I could answer your question but that kind of fluid leak, in the part provided by CPP, is a serious fault in my book. For the sake of others, I would contact CPP and make them aware of your experience. Send them your picture. Please post their response so that we all may be aware. Thank-you.

That is a fairly small picture, but is that the port for a brake pressure switch? If so, the star washer/rubber would have been intended to keep it clean not be a permanent install.

No, it isn't the switch. They show it in the cutaway on their eaby listing, but I don't see any description of it anywhere.

https://www.ebay.com/p/2165604693

I can only offer that most if not all these components are made offshore. I installed some rear wheel cylinders on a Nova some time back that were purchased from a well known supplier. One cylinder failed while bleeding the brakes! The cups did not have any markings inside like the good old US made stuff. It's kind of scary when you think about the potential safety issues with these parts.
Fred

The hole is not threaded or otherwise exhibiting any signs of machining for any instrumentation or sensors. Attached is a closeup of the actual port. A little out of focus, but you can see the plug pushed out of place and what’s left of that washer. Since it’s orientation was directly on the top, I think it just retained moisture in that recessed hole and the star washer simply corroded away until I hit the brakes hard enough to “Phsst” it right outta there.

᠁.and a closeup I snagged off the internet of someone else’s with the plug and washer excavated.

HMM! The ebay link shows it as "currently sold out" and no picture available. Possibly pulled it in response to this issue??

Mine had the exact same leak that was about 4-5 years ago. CPP replaced it under “warranty” as it occurred in the first few months.

I also questioned the reason for the “hole”᠁᠁never figured it out even after an autopsy.

I don't have a CPP proportioning valve in my 55 but out of curiosity I started searching the Internet.

It's called a weep hole and the leak has been noted to occur when the proportioning valve fails.
Comments I have read mentions failure due to new parts residue not removed (extra cleaning needed) before the valve is assembled.
Comments say it leads to wear or leaks around the seals or deformed seals.
Of course it is assembled in Asia and CPP is aware of the problems but it has been going on for many years...FROM WHAT I HAVE READ.
Do your own research or call CPP and ask.

Symptoms are leaking and/or soft brake pedal due to empty reservoir.
CPP has been a good company I really hope they can resolve the issues for the long term.
In the meantime, check your reservoir level before you head out of town. Carry a can of fluid with you.
Don't be stranded in "podunk' trying to get your brakes fixed.

Thanks, Bouymaker.
Unfortunately, you couldn’t carry enough brake fluid to keep a reservoir filled at the rate fluid was pouring out! The only thing weeping was me!

I’m frankly puzzled how a designer would conclude the most efficacious way to alert me of a malfunctioning proportioning valve is to purposefully induce a catastrophic failure of the whole system. Now, if the “weep hole” led to a pressure switch that would turn on the dash brake light᠁ THAT would make sense!

Meanwhile, I already bought a solid brass replacement without this “feature” and installed it.
Greg

Greg, I was thinking of a dual reservoir system where only one section is leaking so at least you could have some braking.
Do you have a dual reservoir?
I suspect you did the correct thing with the brass replacement.

I keeping thinking about brakes failing because a 13 year old kid didn't know the proper way to assemble parts.

Yes᠁ or at least I did until that plug popped out.

And since the probable cause of the plug seeing pressure was ruptured seals on the valve that is supposed to isolate the front from the rear᠁ sudden total loss of brakes!

I hope everybody is reading this post.

First the "no brakes" youtube video of the wreck of a classic muscle car and now this bit of news.
All the more reason to have good working mechanical brakes (parking brakes).

Yeah! They didn’t originally called them “emergency brakes” for nothing!

My ‘46 is all original with a one stage master cylinder and one brake line feeding everything. When I drive it, I’m consciously eyeing that ratchet sticking up right beside the shift lever when braking᠁ especially if coming up behind another vehicle! I drive it as if I expect it to fail! Hahaha!

In my ‘56 on the other hand, it would probably catch me totally by surprise and take me an extra second to react and think to grab that parking brake ratchet under the dash. ᠁coupled with routinely higher speeds it would be a more nerve wracking event. Fortunately, my brakes failed at very low speed in my neighborhood, not out on the highway. ᠁or out in east podunk!!

Final word on this matter᠁

I disassembled the old valve and examined everything closely. The bore looked smooth and clean; no visual signs of any debris or contaminates in the valve or in any of the residual brake fluid. All the seals were intact, pliable and exhibited no obvious signs of damage or deterioration. A great big “dunno” for me.

My recommendation in addition to Bouymaker’s above is if you have one of these, go ahead and buy your replacement w/o that weep hole and store in your truck with the extra brake fluid.

Oh! ᠁and drop us a note from “Podunk”! 😉