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Sounds like you are close enough to phoenix we may wind up at a show or tour sometime. There is a local club, Packards of Arizona I joined the other day. I haven't had a chance to do much with them since I discovered my #8 rod treat, but they seem like great guys. As for treddle vac, I had a power brake company on Grand Ave. (Out of business)rebuild the one I had in a 58 Edsel wagon and never had any trouble. I will PM you contact info in case some local events are going on.

Beautiful car! But, I'd want to keep it that way and junk the Treadle Vac before it costs you your car. I can't stress enough that if you drive you car at all, it's an accident waiting to happen. Manual brakes are safer than that poor excuse of a master cylinder. I know I'm the minority here, since Craig dropped of the face of Packardom, but I know he'd concur with me. It's junk, it's dangerous, and I destroy every example I get my hands on. A modern dual master cylinder is so much safer than that piece of trash will ever be. Nice for a museum car that will never drive again, but dangerous for even a dirt road in the country.

Brian mentioned the Compensator Port Valve and spring. THAT IS the issue i have with the TV master cylinder. If the tiny spring fails then there will be NO brakes.
More common variety of master cylinders, wheather dual or single, can fail too but will usualy give some adequate warning and allow for pumping of the brake pedal to over come the failure. If the spring, or any part of the Compensator valve in the Treadle Vac master cylinder fails then it is NO brakes at all and no interveneing warnings.
Other than the Compensator Port Valve i have no complaints with the TV system. BUT, the Compensator Port is a MAJOR issue.

I believe that little spring/compensator was my issue. When I disassembled it, that little valve,spring, whatever, was sticking up in the reservoir at an angle.

I've rebuild quite a few Master cyls, wheel cyls on other cars, but this is is very peculiar in its operation. Of course, this is the oldest car I have ever had, too!

Maybe someone can explain - how the hydraulic pressure develops with a Seal that is not stationary on the shaft.

Boro -

The Treadle-Vac is actually a very simply and effective design. It doesn't sound like that spring is your problem.

Upon removal of the reservoir cover, you should see the stem of the compensator port valve tipped at an angle. Again, I suggest you check out the 51-54 Packard Service Manual, which is available here, free, to download:

packardinfo.com/xoops/html/modules/news/article.php?storyid=4

At the very least you should download the Brakes section and study the details of the cross-sectional diagrams, but I'll walk you through it.

When the hydraulic plunger is retracted (by the BIG spring in the vacuum cylinder, when your foot is off the pedal), the washer on the end of the plunger tips the compensator port valve open, form the bottom, to permit brake fluid to move freely between the reservoir and the hydraulic chamber.

Whereas a conventional master cylinder moves fluid by pushing a seal down the cylinder chamber to reduce the volume of that chamber (like a piston in an engine), the Treadle-Vac merely applies the princicpal of displacement in a slightly different manner. Yet, you don't have to be Archimedes to undestand it. Fill your car wash bucket to the rim with water, then roll up your sleeves and put your fist in the bucket, all the way down to the bottom, and you'll see how this type of displacement works.

When you apply your foot to the brake pedal, the plunger moves down into the bore of the hydraulic chamber, and the washer moves away with it, releasing the bottom of the compensator port valve. With that valve closed, the hydraulic chamber is sealed off from the reservoir. As the piston moves further into the bore, the volume of the plunger that is introduced in the the hydraulic chamber will displace an equal amount of brake fluid.

Now, with the compensator port valve closed, and all other seals in working order, the brake fluid has nowhere else to go but into the hydraulic lines - ultimately pushing the shoes against the drums. However, if the compensator port valve spring fails to close the valve (or the seal on that valve goes bad), the displaced fluid goes back into the reservoir, which is vented to atmosphere - hence, shoes don't get applied tot he drums.

Get it? (I think you will.)

The real beauty of the TreadleVac design is that you should never need to have that master cylinder sleeved, like so many other cast-iron designs that are obsolete. Beware, however, of TreadleVac units that been salvaged from Packards that have been sitting in a field for a long time. Placed so low on the these cars, moisture from groundwater will take its toll on the die-cast housing. I have seen some pitted badly enough to leak. As such, I would highly recommend that, prior to reassembly, you coat the outside of the master cylinder housing from your car with a paint that is resistant to brake fluid. Check with suppliers like Eastwood for that.

Thanks alot for that explanation.

I do have the manual in hard copy (per se). And, you are probably right about it being ok.

Do you know if that Compensator Port and Valve are available anywhere? Here's a pic of mine. The part that is keeping spring seems to be alittle hammered. Is this Typically of what they should look like in good condition?

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Boro,

On the wheel cylinders, buy them from Napa. That will same you a few bucks and they are the exact same thing (Wagner Wheel Cylinders) you will get from the Packard Part houses. Also is cheaper to buy them brand new, then it is to try to rebuild old ones. If you check the Parts X-ref database I think I may have the cross reference to the Wagner part number.

Boro-

From what I can see of the spring in your pic, I gotta say it looks fairly robust. The springs I've removed from other (unrebuilt) units were much more delicate. I wonder if your spring has already been replaced with some repro as part of a past work by a qualified rebuilder.

The minor kit should include a new poppet for that valve and you should use it. Just hold the existing valve poppet against the seat and depress the spring from the C-washer retainer, and you can slide that retainer out of the groove, near the end of the stem. Then, remove the spring and inspect it for any weak points caused by corrosion (or nicks). During reassembly, be sure to take the extra step or two in the Packard shop manual to install the valve properly and verify that it works. Otherwise, you'll likely end up removing the unit from the car again. (I'm not sure how accessible the valve is with the unit installed. I've removed the reservoir cover with the unit on-car, but the steering column is an obstruction to doing much else.)

Your C-washer retainer doesn't look too bad to me. I suspect any protective plating has merely failed. If you're upgrading to DOT5 (which requires replacing EVERY rubber part in the hydraulic system and flushing the steel lines to remove all traces of DOT3), there will be no problem. If you're sticking with DOT3, then - every few years - you'll wanna siphon the contents of the reservoir and push a fresh pint of brake fluid through the system, via a full bleed, to remove moisture-contaminated fluid from the system - as the reservoir is NOT completely sealed to atmosphere.

Be very thorough about your brake work on any old car - no matter what system it has.