Packard Forum Index » V-8 (1955-56)

Being a new Packard owner and hobbyist, and new to this sight, I thought I would document my body off restore of my 1956 Patrician. As posted on my restore blog, this is my first classic car rebuild. With that said, I am no stranger to mechanics or restores having restored and new built aircraft coming from the Aerospace background. With that said, I have no intentions on presuming to be an expert on Packard restoration; I simply wish to share my experiences and perspectives.

When I took possession of my Patrician, I was told that the brakes were down. Down they were, in fact the brake pedal was stuck hard to the floorboard. With a little friendly persuasion I was able to free up the peddle. The peddle seamed to operate smoothly after that with no sticking. My first thought was to fill the reservoir and see what I had to work with. When I opened the fill cap and got an eye full of hard crystalized brake fluid, I knew in an instant that the master cylinder had to be pulled.

I did a lot of on line research and read many blogs on this site and other classic car sites on the Bendix Treadle-Vac system. The blogs and articles I read were all over the board in terms of people's opinion on them. Good, Bad, Reliable, Non-Reliable, Safe, Not Safe etc. I read many step by step rebuild papers written by various owners as well as was given some suggestion on my blog on a few people who rebuild them. I see a lot of recommendations to have the Treadle rebuilt by a "professional" yet continued to read blogs on how failures continue to occur with "professional" rebuilds.

I contacted a few of these rebuilders and was quoted prices of @ $200-$400 to rebuild. Having looked at the prices of rebuild kits and various components, I thought to myself, there is no way that you would be getting a complete rebuild of all soft and necessary hard parts at these prices. When I ask, in detail, I am told that the pistons are not disassembled and gone through. To me, that raised some concerns, especially with the high failure rates that were being reported in the blogs. One thing I noticed in all the blogs, at no time did any of them give the condition of the mechanical parts of the Treadle when the failures occurred. In not knowing this, how can anyone truly make a sound judgment on if they are an acceptable master cylinder or "Junk". Common sense tells me cars drove all throughout the 50's and there is no data that I could find anyway on massive Treadle failures. So, wrenches in hand, my rebuild of the Treadle began.
Upon basic disassemble into the three major subgroups, piston, vacuum canister, and the hydraulic assembly. The very first thing I noticed was that the vacuum canister was heavily pitted on one side of the can from top to bottom. Both the Packard Service Manual and the independent rebuild instructions suggest honing the can if needed. After honing, the pitting still remained. The independent instructions stated that pitting would not be a problem. Again, applying common since of piston actuated cylinder, I reasoned with myself how this can possibly be acceptable. My past experience in hydraulic cylinder rebuilds tells me otherwise. The Packard Manual also to me was clear on the allowable conditions of acceptable wear of parts and the can just did not pass that test. I was able to locate a good can from a person on this site and purchased the replacement for $45.

I purchased a rebuild kit from one of the two big names in Packard parts for $95 and the kit is sold as rebuild kit for both Hydraulic and Vacuum sides of the Treadle. I received all seals, O-rings, gaskets for the hydraulic side. This was a very simple and straight forward rebuild. One thing I learned upon further investigation is that Bendix actually made three variations of the check valves. Most that I see sold and the one that came in my kit has the small wafer disc with four holes and the rubber piece. Mine however, is the thimble or hat type. The rubber piece is not an exact fit for this style valve. Question: Have people been using the rubber piece anyway with the thimble or have they replaced the thimble with the wafer? If so, does this change the function of the Treadle and could this be a possible cause of some of these failures? Don't know, but I did some digging and ordered the right rubber for my thimble style valve. In the rebuild kit, I also received a new vacuum hose, piston wick rope, and modern foam to replace the horse hair in the vents. At this point, I could have replace the leather piston cup and just put the Treadle back together. But again, common sense said wait, what does the piston do? You have pressure differential dynamics going in inside the piston compensating for vacuum and atmospheric pressure. If hard brake fluid craped up the hydraulic side, surly there has to be crud in the piston no to mention three very important parts that from my understanding do not normally get looked at in rebuilds.

Upon the disassemble of the piston, yep, there was some hardened contaminants that I am sure if left untouched would have caused a future failure but this was not my main concern. I found three things inside the piston that I am one thousand percent convinced would have caused a very quick if not immediate failure of the Treadle if installed as is. First find was the vacuum poppet compensation stem and journal has enough corrosion on them to not freely operate correctly. 2nd, the rubber on the vacuum and atmospheric poppets were extremely deteriorated and deformed. The rubber was a soft mush that would not have sealed the slightest pressure. The poppets were not a part of the rebuild kit which I found odd, I mean if you are going to rebuild something, rebuild it not just what is easily or convenient. The kit comes with the internal piston gaskets so why not the rest of the components? The poppets are readily available and I purchased the set for $30. In addition, the piston diaphragm was in the same decay as the poppets. There were no tears or holes but the rubber was extremely soft and spongy. Again, no something I would want to reuse. Diaphragms are also readily available for $95.

So, by being a little anal, I did a 100% teardown and inspection of every part and component, I replaced anything that was questionable (coincidently that is exactly what the Packard Repair Manual says to do too) So for approx. $250 and few hours of time well spent, I now have an fully functioning Bendix Treadle-Vac that I am confident will operate reliably as designed. I am lucky enough to live 10 miles from the Bendix (now Honeywell) plant in South Bend. A good friend of mine's father worked 40 years at Bendix as an engineer and still has some old tools around the house. One being a master cylinder tester, the test says we are a go after the rebuild so I will let ya know how I made out. He is confident in his old products. I do feel properly repaired and maintained it should operate safely as intended.

Again, this is my experience and perspectives; I am in no way saying I am right or that anyone I have talked to or dealt with is incorrect.

Happy Restoring.

i have questions about my rebuild, since it came back with a bent rod. the one that connects to the brake pedal.

Troy, Good post and very informative, I like yourself bought the rebuild kit plus a new piston/plunger and rebuilt my BTV but on strip down of the vaccuum piston found the poppets etc to be perished. I could not locate the parts required anywhere and was informed only the so called rebuilders have these parts.
I have since changed the brakes out on my car for a manual master cylinder arrangement with a remote mounted booster but would like to complete the rebuild of my BTV someday just in case.
My question then is where did you purchase the vaccuum section poppets and piston diaphragm..?
Regards,
Dave.

Nicely done. A few observations: The failure mode that everyone is concerned about is of the hydraulic portion. I fully agree that the vacuum side needs to be rebuilt and do so on the units that pass through here.

I don't fret much about pits in the vacuum cylinder unless they cover a wide area in the working zone. It operates at the equivalent of maybe 7 psi during a panic stop, and the wiping area of the leather seal is quite wide. Even if the vac side were to fail utterly you can still stop the car though it is not fun.

The style of check valve doesn't seem much of an issue as long as it maintains the the residual pressure that drum brake cylinders prefer. The internals of the master cylinder don't see that residual pressure in any event.

The important failures are hydraulic ones and that is addressed by a careful workmanlike rebuild of that portion, as you noted. I am quite anal about having a perfectly smooth hydraulic piston and carefully seating the seals in their bore. That, and being careful with the installation of the compensator valve.

Look forward to the results of your test.

As Ross indicates be careful about fitting the compensator valve. The rest of the brake system (lines hoses wheel cylinders etc) should also bekept 100% CLEAN!!!!!! Any debris that could possibly hold the compensator valve even just slightly open will cause a total and complete lack of hydraulic pressure. Bottom line:
The hydraulic master cylinder of he BTV IS extremely sensitive to debris because of the compensator valve. Other more common and widely used master cylinder designs do NOT have compensator valves and are therefore not as sensative to debris. Not any where near as sensitive to debris.
Threfore BTV has a shortservice life and high maintenance master cylinder.

Quote:
I doubt it.

I, too, questioned this substitutiton the very first time that I rebuilt one of these units, over two decades ago, using a repro kit. Yet, I went ahead and used the wafer type residual check valve in place of the original thimble style.

More recently, I learned (from a thread on Bendix Treadle-Vac Restoration in a M-E-L forum) that this was a subsequent (third) design from later production units (c.1959/60). Whether that's a Bendix-sanctioned replacement or not, I don't know, but it's been in place and working with no problems in my cars.

Here's what we really need:
A conversion kit or service to modify the oem BTV master cylinder to work like more common master cylinder design thus eleminating the compensator valve.
Eleminating the compensatoe.valve will eleminate the BTV sensitivity to debris.

ALSO an atmospheric diaghram to seal the reservoir ala modern master cylinder designs SINCE THE LATE 1960's.

Quote:
" Common sense tells me cars drove all
throughout the 50's and there is no data
that I could find anyway on massive
Treadle failures. "

That argument does not hold for everything. Consider olds diesels ca early 1980's, vegas, corvairs , disappearing tailgates, fords with mechanical brakes thru AS LATE AS 1938, recent run away toyotas with sticking gas pedals that the experts blamed on driver error, and the list goes on and on and on.

With that philosophy we should all drop internet and go baxk to smoke sinals and beating on drums????

To the best of my knowledge there was never a PUBLIC ANNOUNCED RECALL of any kind prior to the late 1960's. So yes, would not find any 1950's records of failures for the btv.

still want to know where you got these extra parts that are not in the rebuild kits.

In response to where I found the Treadle Vac Parts, here are two sources.

Max Merit

all parts in stock immediate shipment

1.326 part number 474034 $95
1.358 part number 6484066 $95
1.3541 Atmospheric Poppet $15
1.3542 Vacuum Poppet $15

You can also talk to Charod at Kanter Packard Parts Department.

They have the following Kit available

Kit price is $95, Kit consists of the following:

1.3541 Atmospheric Poppet
1.3542 Vacuum Poppet
1.3548 Vacuum Poppet Spring
1.359-Vacuum Diaphragm Gasket

Lead time is about 1-2 wks delivery.

Happy Restoring

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