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The other day I was driving my 52 250 and up until this point the brakes worked fine, never failed once. I would test them in the drive way and they were good. I pulled out of the driveway and drove a short distance and when I rolled down my driveway again I had brakes but when I tried to stop I completely lost them. Once I came to a stop I cut the car off and back on and the brakes were fine. Anyone willing to help would be greatly appreciated. I’m a new to the mechanic game but figured I would come here for help.

Do we assume you've checked the fluid level? If not, that's a place to start. How long since the system was drained, flushed and refilled?

Manual or Power Brakes?

If Power, perhaps the compensator port/value had crud that was preventing it from sealing.

They are power brakes

I checked the fluid and it was a touch low but nothing crazy

Kev is probably correct in that the compensator valve is suspect if the brakes fail at times and then work again. This is a critical valve and consists of a spring held single piece of rubber that the end of the ram or piston bumps against in the released position and normally holds slightly tilted and open so fluid can freely enter and leave the pressure side. When the pedal is pushed and ram or piston moves forward to displace the fluid, the spring can then pull the rubber straight and upward so valve seals the port. The increased hydraulic pressure in the master will force it tightly closed as long as there is a good seal to start with.

If the spring is weak or if there is any kind of contamination, old congealed or crystalized fluid or anything else floating in the fluid that happens to land on the seat as the valve is closing the seal is lost and there will usually be no brakes because whatever hydraulic pressure is being generated in the master just pushes fluid back into the reservoir and not out to the wheels. When the pedal goes back to the released position and the valve opens again the debris might move off the port so the next time you apply the brakes everything works fine. This action has resulted in the bad name Treadlevacs have of stopping at one light but not the next.

If the system has not been flushed for awhile I would carefully examine the condition of the fluid to see if this could be your problem. The debris might not even be seen because it could be floating in the piston side below the valve and not in the reservoir. Even better would be a rebuild particularly if the unit has been sitting and is now being placed back in service.

Here is a page from the Easamatic Training Manual. This book was written when your 52 unit was used which has a slightly different power or vacuum operation than later units. You can download the manual from the literature section and photos are much better than those in the 51-4 service manual.

Attach file:

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  compensator valve.jpg (302.80 KB)

It looks like clean fluid would be an absolute must.

Would changing the type of fluid make a difference and I know you mentioned a rebuild but how would I go about that. I’m very green in this field so where would the valve be?

Changing the fluid would probably be a good idea but not to a different type. Stay with the DOT 3 or 4 which should be what you have unless there has been a rebuild or work done. If that is the case there is no way of telling from a distance other than glycol 3 or 4 fluid is typically clear to amber or yellowish in color while DOT 5 or 6 silicone based fluid is generally purplish. Going from glycol based to silicone based requires a complete flush and cleaning of the system since the two cannot be mixed. There are many opinions on the merits of both types but some mfgs do not recommend silicone in the older still original systems.

As far as a rebuild, while the Treadlevac is not a difficult unit to rebuild and the critical hydraulic parts are included in rebuild kits, there are some subtle things to look for when it is torn apart and some things to watch out for when going back together. Pitting or corrosion in strategic spots in the pot metal casting or on the ram is one of the most important things to look for. A clogged relief port is another. If you miss something the unit could be no better after the rebuild than it is now. If you are not familiar with the system and are new to mechanical things, unless you have a mechanic friend to give guidance and advice perhaps learning on a power brake unit is not the safest thing to start with.

I am not saying you cannot do a good rebuild and definitely do not want to discourage trying. If you are extremely careful and follow the procedure in the service manual it should go well. If there is doubt, I would probably stay with getting an already rebuilt exchange unit from one of our vendors. Kanter, Max Merritt, or Tucson Packard will stand behind their rebuilt or exchange units whereas some who have splashy ads in various publications advertising rebuilds for all types of units have been found by others on the forum to be less than adequate both in workmanship and taking care of any issues that might come along.

The valve in question is circled in red above and is easily accessible after taking the reservoir cover off. The assy just unscrews from the casting. Unfortunately, other than seeing the condition or if a chunk came off the rubber valve not much more can be done without taking the rest of the unit apart.

You also have to scrupulously clean the old system in order to switch to silicone (DOT 5) to prevent cross compatibility issues. Usually an alcohol flush. Not sure the old parts are compatible with it, certainly wasn't around in the '50s, so consider maybe jumping from one fiasco into another.
DOT 3/4 usually just flush out with extra bleedings. It's only good until it goes a darker straw color. There's a test/testers for it, free of particulate, etc. Much easier to just replace all, why chance it?
Fluid quality issues don't usually manifest in complete or intermittent failure modes. Something's sticking or not functioning properly at the master. If it's a wheel/line issue usually a couple will still grab. You said it resumed on its own - another clue.
I don't like chasing these safety systems one at a time or over the internet.
I go over the whole brake system so I have confidence I've found the issues and repaired them.
I'd start with the wheels, pull each one, and clean and inspect the linings, cylinder, etc and the hoses/replace/repair as needed, and flush or replace(rusty) the lines while disconnected. Take the booster/master off and put on the bench to check it out.
Some of these old early systems were notorious, and since they don't have the dual master systems, you go without brakes on failure mode. That's what lead to the dual systems. Lots of people had to go through windshields to get them to change and only after the law got after them. Poor reliability from the get go.
They're plenty of brake rebuilders; Whitepost, etc out there, if you're not sure. There's a 5050 chance they'll do it wrong anyway. So make sure they test/can test it before returning. They'll bock because they have to clean it before shipping.
I haven't messed with this "P" unit so take HH's advice. I replaced the '49 master with a repro and it was not that good quality either.
There is a bit of liability if you work on it - unqualified - and cause an wreck after. Insurance may not pay. I sent my Cad out for upgrade because I didn't want the liability. Once you cross into the DOT line, it's a different ball game.