Packard Forum Index » Modification Discussion

First up will be history & personal experiences by Craig.
Easamatic power brake was an option on Packards from 1952-56. It was actually a generic system called Treadle-Vac manufactured by Bendix mounted on the floorboard directly under the brake pedal. The Treadle-Vac was also available for various years on many other cars of the 1950s (all GM, Edsel, Lincoln, Mercury, Hudson, Nash and even Mercedes). The Treadle-Vac was superceded in 1959 by most manufacturers by the familiar Delco-Moraine power booster mounted high on the firewall.

I believe that there was a good reason why the Bendix Treadle-Vac was superceded by the Delco-Moraine power booster: The Treadle-Vac was failure prone! I personally have had three failures of professionally rebuilt Treadle-Vacs. One failure was without warning and total, i.e., NO BRAKES while driving in traffic! Fortunately, I didn't hit anything and got my 1955 Patrician (slowly) stopped with the parking (emergency) brake. I know of five other Packard owners who had the same kind of failure. Also of concern is the expense of having the Treadle-Vac rebuilt (several hundred dollars).

These reasons are more than sufficient motivation to find a better solution! However, telephone calls to several aftermarket manufacturers all resulted in the same "NO" answer to my question, "Do you have a replacement for the Bendix Treadle-Vac?" I decided to pioneer a solution myself during my Panther Project!

After some research on the web, I found that a 7-in booster for a street rod application from Master Power Brakes (MPB) would probably work and ordered same.

See1956packardpanther.com/powerbrakes.html website for details of installation including a reworked brake pedal leverage.

I owned a 56 400 in the early sixties. The seal between the hydraulic cylinder and the vacuum canister failed. I bought a kit and rebuilt it myself. It never failed again. Memory says that the kit contained a new compensating valve and spring. I purchased a 56 400 in 1972 and have had it rebuilt by a professional rebuilder. He replaces all the components that could fail including the small spring that causes the compensating valve to close. I have never heard one of the complainants of the TV system determine WHY their unit failed. I would like to hear one of them say they tore the unit down and discovered that A or B or C was the component that failed. And then verify that they had replaced that component when they rebuilt it. That small 50-year old spring that has been sitting in water-contaminated brake fluid for 50 years has to be replaced. If not, it will fail. When rebuilding any system like the TV, you must replace all such components.

One need only look at the few bulletins Packard issued, via this site's Service Index feature, on the Easamatic brake unit to see how relatively trouble free the BTV was.

Most of the bulletins are what I'd class as "new model info" - typical with any new technology presented to the dealer body. I only saw a few mechanical issues listed and only one (the operating rod pulling out) that could lead to a catastrophic episode, but that was encountered very early in the timeline. Sounds like typical teething pains to me. One could encounter the same or even worse in trying to retrofit modern aftermarket equipment.

I agree that most of what we are seeing is due to sheer old age and exposure to the elements, but also some incompetent rebuilds. I think you'd be able to sell a lot more of the repro (minor) rebuild kits to DYIers with more confidence if only the compensator port valve spring were also included.

Change or Not - The case for maintaining originality. Some buyers/owners of collectible cars want a Packard body on a new Chevy Yukon frame with all the modern amenities; others want to experience what it was like to drive and maintain an older car as they were built. Some potential purchasers see modifications as detracting from value, others see it as adding value - each owner needs to determine for himself where in this mix he wants to be. The Bendix TreadleVac was the OEM power brake unit for many car manufacturers including Chevrolet, Cadillac, Buick, Pontiac, Oldsmobile, Lincoln, Mercury, Edsel, Hudson, Nash, and Mercedes-Benz (gullwings no less). It was introduced about 1952 and I believe Lincoln was the last to use it in 1961. The unit was installed on tens of millions of cars over nearly a decade, without recall or redesign. Mounting particulars varied but internally they were all essentially identical.

Packard's service letters do not indicate a history of problems or failures with the unit. The technical threads of other car clubs and associations that used the TreadleVac are relatively devoid of comment of problems. A few Packard owners have reported catastrophic failure, though we have not benefited from knowing the quality of the core, the repair/rebuild history or the results of an autopsy to indicate the mode of failure. According to whom I believe to be the best of the TreadleVac rebuilders, problems are no more common than with any other type of single master cylinder system.

I believe the facts point to the TreadleVac as being a completely reliable power brake booster, though of course lacking the extra security of the later "dual cylinder" systems. However, I would NOT recommend that owners wishing to retain the TreadleVac rebuild their own units several reasons. First, it's just too important a part to not entrust to a professional who specializes in them. Secondly, there are "rebuild kits" available, some dating back to the 50s which should never be used, some new and fresh such as the Kanter kits, but the rebuilder cited above states that he has about 25 other individual parts made for his own captive use in each rebuild, these parts not being available to the do-it-yourselfer.

My on this subject, starting here with the second post of the thread on this forum.

Post #4 on this thread.

Post #5 on this thread.

All of this thread.

Another good thread extolling the "virtues" of the Bendix Treadle Vac

I've tried to give a good comparison of "pros and cons" with these links. Some like them, some don't.

It's not just Packards that they fail on, it's everything else too. I cannot, will not, and have not recommended the use and restoration of these units, they are much too dangerous. Craig's conversion is the best way to go if you don't want to cut up the car any, Paul's and mine are the best way to go for total updating of the master cylinder. I like Paul's use of the Hydro-Boost setup, but I like my location better. If I were to do it all over again, I'll be using the Hydro-Boost.

Quote:

That last line is of central importance to this discussion, IMO. The TV is probably as reliable as any other single MC braking system... but that's the point: it's still a single system, with no backup. This is a drawback for anyone driving a vehicle that predates the standardization of dual braking systems in the late '60s. This includes manual as well as power brakes.

Now, if you could, or would want to, somehow modify the T/V to operate in a dual braking system, it would probably be as safe as any other dual system.

Also, to get the most safety benefit from a dual braking system, you need a warning-light to tell you when half the system is down (you can drive a long time on half your brakes and get "used to" the difference, mainly when it's the rears that have failed).

I'd be interested to know if the conversions some have made to dual braking have included a warning light system, and if so, how they did it. Do new off-the-shelf kits include this feature?

A warning lite?????? What if the lite burns out????
Is there someone who needs a Christmas tree to suddenly lite up just to tell them that their brake pedal just wnet to the floor????

Dual cylinder vs single. Why not make it quadruple??? Have 2 wheel cylinders per wheel and seperate MC's. One pedal actuates BOTH mc's. Thus 2wo seperate hydraulic systems acting independently of each other.

NO,WAIT A MINUTE!!!! maybe 18 wheel cylinders ......

This has become ridiculous. The single cylinder is just as safe as the dual. OR the dual is so marginal in its 'extra safety" claim so as to be neglegible.

The problem with the BTV controversy is that over the last TEN YEARS only TWO TECHNICAL (do i have to repeat T_E_CH_N_C_A_L) issues have been raised regarding the BTV.

Thus far i have only seen TWO statements in this thread that are constructive:

From post #3 above:
RB said: "I have never heard one of the complainants of the TV system determine WHY their unit failed."

And BH indicating the spring issue.

******** --=*=-- UNTIL RANDY BERGERS STATEMENT ABOVE IS ADDRESSED THIS CONTROVERSY WILL RAGE ON JUST AS FRUITLESS AS IT HAS OVER THE LAST TEN YEARS THAT I KNOW OF. ***************** --=*=--

This has become ridiculous. The single cylinder is just as safe as the dual. OR the dual is so marginal in its 'extra safety" claim so as to be neglegible.

PV8, I couldn't agree more. And perhaps you'd agree that dual steering systems aren't needed either? As others on this site have no doubt done as well, I've driven hundreds of thousands of miles with single-master cylinder cars and never had a failure. Never had a friend that had a failure. Never had a failure with 1/2 of a dual system. Of course anything mechanical can fail, but I'd bet that those failures that did occur were with poorly or non-maintained cars.

In any case, to each his own...