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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I'll try Mr. PB suggestion and also look at yours. Thanks for the input. Ron

Thank you for the help. I'll give it a try. Ron

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:

https://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.

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.

Since you've just been thru the entire fuel system, I'd suspect poor fuel delivery as a good candidate for your problem. Fuel pumps would much rather suck air than pull gasoline 15 feet or so from the rear tank, so I'd inspect every connection between the pump and the tank for a loose connection, and also check the gasket at the pump sediment bowl if so equipped. Don't know what "same car" means so can't be more specific.

If its not fuel, I'd suspect a failing ignition coil; these generally only act up when they get hot. Just go buy a universal ignition coil and wire it up temporarily and recheck.

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.

Same car. It will run ok when it starts, but after about ten minutes, it sputters and dies. I've never had this issue. Carb is rebuilt, new gas tank, new fuel pump, clean filter, clean, fresh fuel. Points are set at .017. Has new points and condenser. Any ideas?

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.

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.