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We would like an additional forum member to submit their non-operating or poorly operating BTV. We wish to do a failure analysis and will rebuild it and return it for free.

Just last week we had a walk-in customer whose power brake unit failed on his 57 Oldsmobile. The car sat in Cuba unused for 30 years and then an additional 6 years here. He got it running and soon after the unit failed....it was a Delco Moraine and it was full of gunk.

what about units that are in pieces because the owner likes taking things apart in preparation for rebuilding them, but never got around to ordering the rebuild kit because they feared over it sitting after rebuild because the car isn't ready to go just yet? lol! if so...uhhh I got one of those he said embarrassed like lol!

unit sat in field for 15 years and then in my garage for another 5-6 before being taken apart. no idea if it worked before or not...didn't try brakes when I got the car. started motor and then just started taking car apart.

https://packardinfo.com/xoops/html/modules/newbb/viewtopic.php?topic_id=653&viewmode=flat&order=ASC&type=&mode=0&start=1690

SORRY NO, IN ORDER TO DO A FAILURE DIAGNOSIS WE MUST SEE A RATHER RECENTLY FAILED UNIT. DISASSEMBLED, WEATHERED OR ANCIENT UNITS CANNOT BE DIAGNOSED. WE'LL LEAVE THAT TO THE ARCHAEOLOGISTS AND THEIR CARBON 14 DATING.

FRED

I like what you are doing.

It seems like the only way to see why there was a failure.

I don't know how many units have been sent in for this, but do you see any models performing worse than another?

The 55-56 parts book indicates 3 different repair kits, P-2, P-3 for 55, an unmarked unit for 56.
https://www.packardinfo.com/xoops/html/downloads/partslist5556/Repair_Kits.pdf
It shows only 2 units P-3 for 55, unmarked for 56
https://www.packardinfo.com/xoops/html/downloads/partslist5556/01_Brake.pdf

The 48-54 parts book only shows 1 repair kit.
https://www.packardinfo.com/xoops/html/downloads/partslist4854/48-54_Repair_Kits_Sets.pdf
It shows 2 units one for 25th, and one for 26th and 54th series.
https://www.packardinfo.com/xoops/html/downloads/partslist4854/48-54_Group_1.pdf


What changes/upgrades are there between these units?

And I'm also curious if there is any chance of a correlation of failures between years. When the rash of reports of sudden failures seemed to be a daily topic it appeared like it was mostly happening to V8s. Occasionally an earlier car was mentioned but not that often.

Possibly V8s are driven more so more chance of failure but with far more S8 units being produced that doesn't seem logical. Have wondered if V8 units being a few inches away from the exhaust manifold heat instead of several feet away could have something to do with seemingly more V8 issues.

Fred-

If this is of any help in your quest.

Just took in a customers 56 Pat. TV failure straight to the floor. When I picked up the car made a few inquiries leading up to the event.

No prior issues, always stopped well. Last system flush greater than 3 years.

At Pick up, TV was again operational and great operation with very light pedal pressure. Theory: expecting to find some particulate matter in fluid and must have temporarily held the compensator open causing customer floor drop.

Tear down- unit was pristine internally. Every seal, rubber, leather components undamaged and looked to only be weeks or months old.... Absolutely no pitting or wear on hydraulic stainless piston, it too looked new.

Two issues found: Aged fluid just started to breakdown forming hardened particulates in the reservoir. 2nd, someone had used JB weld and sealed off the vent port. First time I have seen that, I have had a few units brought in that were blocked off from use of a gallon of silicone ( we know who does that)

Lines flushed wheel cylinders rebuilt, a new Kanter kit and TV is back in action.

My unit is complete. It was not holding. Pedal would go to floor.

I got acore from mike. And has ed strain rebuild it. So far ok. I use silicone..

I have been following the many discussions about the Bendix Treadle Vac brake booster . I have no direct interest as my Packards pre-date any form of brake boost, however, I cannot understand how any manufacturer of a brake boost system could offer a unit where its failure, for whatever reason, causes brake failure. As much as I am obsessive about keeping them authentic I think this is an issue where there is a strong case for a replacement booster with a unit where loss of boost leads to no more than the need for a heavier pedal force.
Just my 2 cents worth - with apologies for adding to the controversy.

Quote:

Where I am confused on this subject is a statement like such.

"I cannot understand how any manufacturer of a brake boost system could offer a unit where its failure, for whatever reason, causes brake failure."

Even though your master cylinder system pre dates the BTV it can still experience a similar failure as could any make or model of vehicle pre dating the advent of the tandem master cylinder (starting in use around 1965???) Whether it be a power unit or manual set up you had one line out and a single check valve in place. If a valve or a seal were to fair then a loss of brakes would happen regardless of what type of master cylinder you have. What Fred is try to make clear is that it is not the fault of the units design that is the main cause of failure but the lack of maintenance and age. All items over time wear and require rebuilding. If the BTV was such a dangerous unit then why are there no TSB from the beginning? Or production halted? They were used in more than just Packards I oversee many other forums for Kanter such as Olds, Buick, Cadillac, Chevy and Pontiac many of which used the BTV and none of these forums have had such postings to this extent. Many of the post normally ended with a statement stating the key to a proper working BTV is cleaning and maintenance.



Thanks
James

Apparently there are -- or were -- some disgruntled BTV posters in other forums. There is a Chevy vendor who sells a modern replacement unit and leads off the description by saying his unit is "a direct replacement for the dreaded Bendix Treadle Vac". I would imagine the term "dreaded" might be for effect but at least it shows the subject was discussed somewhere.

I don't have photos or much info on all the other mfgs that used the BTV but from what little I have found, Packard so far seems to have been the only mfg who mounted it low and at the end of the pedal using the direct 1:1 ratio. That alone is why the modern so called direct replacements won't work for us.

I am also curious if anyone else mounted it near a heat source as Packard did with the V8s. Chevys were high on the firewall with a good ratio to their pedal, another mfg mounted it midway on the firewall, and still another near the radiator with a long rod connecting the brake linkage to the unit.