Packard Forum Index » Post-War (1946-54)

Dear 55:

The Treadle-Vac doesn't use a typical piston and seal. It uses a ram (power piston) that displaces fluid the same way as a forklift.

The large diameter of the compensator valve applies Pascal's principle to amplify the pressure on the compensator port seal. That is why it looks so big.

If your guy doesn't do the Treadle-Vac on a regular basis I would go with one of the sources recommended here. I got a call once from someone who's 56 Oldsmobile with Treadle-Vac lost it's brakes. The unit was done by an outfit that rebuilt lots of boosters, but not a specialist. They had the seal in backwards.

I think it's better to send all the business to a few specialists because that way they can stay in business and reduce the possibility of catastrophic failure.

Tom,

I have seen the master cylinder piston referred to as a "Hydraulic Plunger" (in a Packard cutaway drawing), and as both a "Hydraulic Cylinder Piston" and "Master Cylinder Piston" (in the '54 shop manual). I suppose a "power piston" says about the same thing, but perhaps they wanted to avoid the "power" reference so as not to infer that the piston was actually pushing the fluid, rather than just displacing it. "Ram" I have yet to see in print, but I know what you mean. Heck, they probably use power piston somewhere, too.

Obviously the exact labels of various parts were still in the works. It would be nice if they had some internal consistency, at least.

I think your posted photo puzzled me because I couldn't tell the size for sure. I believe it shows what they refer to in the shop manual as the "valve rod and boot." They don't have a picture of that, but what they have pictured is the "valve cup" and "cup retainer spring." Please correct me if I'm wrong.

Note to all: These parts are TINY! What would you estimate the diameter of the boot and length of the rod in the photo is, Tom?

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HH,
Would the unit in my '54 be one of the "first units" and thus not need this mod to the gasket? Or would the same caution apply?


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Hank,
Ii have Ross' instructions, and I'm sure their good. I just wouldn't trust anyone who was trying this for the first time. I wouldn't trust myself to try it at all. My rule of thumb: If it makes it stop or steer, I don't mess with it. Other stuff, like making it go, I'm usually OK with. Just my preference.

WILLIS,
I've thought of changing to manual brakes, but I've been told it's major surgery.


Also, can anyone, weigh in about the need to "re-sleeve" the bore with .304 stainless as one builder suggested to me. By this, I believe he means the bore that the "hydraulic cylinder piston" goes through.

Thanks. Stay tooned...

I hadn't worked on cars for over 40 years when I worked in my Dad's shop. The change over was not difficult and I got my instructions and standard brake mechanics on this site from the same people your are talking with about the Easamatic system. It just seemed more logical to me to do this one time and not have any risk or cost. I was replacing everything in the brake system so the cost of going to standard brakes was actually cheaper than having an Easamatic rebuilt.

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The first units when introduced in 52 had a lower port opening just under the lid and in the reservoir. I don't know when the change was made to the next version. You will have to look at yours to verify but most likely it is the one in question and needs to be checked.

Here is a compilation of photos posted over the last 2-3 years detailing the issue. Some photos mine, others by KevinAZ. Top row shows items for the flat lid. No gasket over the port because there was no need with the lower opening.

Lower photos show the different gasket used with the port change. Probably supplied by Bendix & has been found many times on supposedly never touched factory original units -- and the port was blocked by the lid. The other photos show port all the way to the top and one version lid out of several available. Other mfgs used different lids to accommodate the raised port design. Packards original style flat lid totally blocked the port opening.

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HH,

Thanks for the photo. The different pattern of the holes is easy to see. I would think an experienced rebuilder would be able to see when a gasket is covering a port.

This really gets my attention. I wonder how many "failed" rebuilds are due to this misalignment or just plain wrong gasket?

I for one would be very suspicious of putting a gasket on any lid if the gasket ended up covering a hole or port.

The problem with this situation is, I could send out my booster for rebuilding and get it back needing a replacement or re-engineered reservoir lid gasket. I'd rather get it right the first time!

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You'd think so but in one of the threads from a couple of years ago when all this was under discussion, Fred posted a photo of one he had received back for evaluation.

He found some "rebuilder" had actually filled the port with silicone. Said they had also used the stuff in other places. Really makes one wonder about what qualifies as a rebuilder.

I'd stick with those who come recommended -- Ed Strain, Max, Kanter, and Midwest have all received good marks from people here.

Ross has rebuilt several with great success from what I understand as well.

At this point, i would recommend to order a completed unit (NOT a kit) from any of the NAMED RECOMMENDED sources above.
Install it and keep us posted.

PackardV8,

Thanks for the message. I am interested in getting my own, present booster rebuilt and returned to me. That would be my first choice.

Midwest Power Products and Ed Strain both offer this, I believe. Also, I think Ross rebuilds originals, but I've heard that he may want to have the whole car and do the R&R himslef.

Max Merritt and Kanter appear to have off-the-shelf rebuilds, which I believe require a core replacement.

I suppose that sometimes it's up to an individual rebuilder whether to restore a unit supplied by a customer or replace it with an off-the-shelf rebuilt, for example if the original is beyond repair, or for faster turnaround is desired. But I wouldn't know for sure.

I never anticipated buying a kit. Then I'd just have to find someone to put it in, and maybe tell me he had some issues with the kit I'd bought.

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OK, a question about this PM stuff. If can't find a person's avatar to click on in a post to get to their profile page, what's the quickest way to find it? Searching for an avatar never works-- such as typing "Ross"in the Search window and hitting "Find" (with the Forums search box checked ) It finds some stuff, but it doesn't find Ross.

How do I quickly find somebody's account to send them a PM, when I know their avatar already?

Usually, I just hunt around for one of their posts until I find one and then click on the name in the bar over the post.

All these years, and I haven't figured this out.