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I recently purchased your rebuild kit & 5 1/2" leather seal for my unit followed the instructions, installed unit and still have a hard peddle.I have replaced all parts related to the braking system shoes, linings. lines hoses, etc. I even bought a rebuilt unit from Tucson Packard and have sent it back to Sandy 3 times,he has tested the unit and each time I have the same results,HARD BRAKES, I have also checked the unit as Sandy has told me with just the vacuum line on and with no effort it sucks the rod right in, when I install the unit and connect the fluid lines I am back to square one HARD BRAKES, even standing hard on the brake peddle I cannot lock the brakes up. Would appreciate any help from anyone who has had a similar problem. Thank You, Peter

Have someone open ONE wheel cylinder bleeder screw WHILE u push the brake pedal. If the brake pedal goes to the floor real fast then close the bleeder screw and test another bleeder screw on another wheel until there is a difference felt at the pedal. Which ever bleeder screw that opens and produces noticable resistence to pedal pushing will determine which wheel/brake line is causing problem.

Did u replace ALL THREE RUBBER hoses in the brake line too????

IMPORTANT: Once the pedal goes to the floor DO NOT LET UP ON THE PEDAL UNTIL THE BLEEDER SCREW IS CLOSED.

although you have said you have replaced all related items, I'll go over possible causes. I suggest you go to THE source, the Packard service manual. Saves time, effort. speculation etc etc.

If the car has hard brakes and no single wheel locks up. it could be the power unit, but that is pretty well eliminated with all the units you have tried.

Vacuum source to BTV-vacuum valve at manifold
All wheel cyls frozen
Rubber hoses collapsed
Glazed linings
Linings having minimal contact, usually in center due to drums being machined too far oversize or incorrect thickness linings

good luck

Hey all, I've been reading with great interest in the Treadlevac problems and do hope someone comes up with a solution or retrofitting of a better device(s). There is on ebay a power booster for a buick and while the booster is definitly a bendix device the master cylinder is very odd looking. I recognize the electrical "stoplight" switch but the other ports, holes, and configuration is a bit odd looking. Maybe it could be bought and seen what is different compared to the Packard's master cylinder?

ebay:
packman711:
1956 BUICK BRAKE BOOSTER RAT ROD HEAD LIGHT TAIL TRIM

It appears to be Buicks version or copy of the Treadlvac. They had one version in 53-4 and then a different power unit design in 55-56.

There is also a Moraine variant of the Treadlvac with some differences in both sections used in some mid 50's cars. It is interesting that so many cars used similar units. I've always been curious why one unit seems to be used partial years here or there or in this model or that. There seems like a lot of interchange or switching across the full line and even full year.

All are similar in that they use the ram type hydraulic section instead of the piston/cup and differ mostly in the seals and vacuum section. There are a lot of variations in that vacuum section thru the years. The 55-6 Buick unit appears similar in vacuum design to the later hydraulic reaction Treadlevac units.

If you have access to the old Motors Auto Repair Manual, the 20th edition covers all of them in some detail with illustrations.

The Buick ebay item 150542291995 is not a Bendix Treadle Vac and does not contain any Treadle Vac parts, it is a 1956 Buick Delco Moraine unit which is very close to the 1955 version. Teh '53-'54 mwere not Bendix units either.

Treadle Vac uits ha=ve an aluminum maser cylinder casting and will have Treadel Vac cast into it. Delco units have a xcast irom master cyl and have a part number cast into it starting with the digit 5.

Despite what any Motors Manuals say the Bendix Treadle Vac was used on Buicks in 1957 only.

AGAIN

THIS WILL BE THE THIRD TIME I AM POSTING OFFERING A FREE COMPENSATOR VALVE TO ANYONE WHO FEELS THEIRS IS DEFECTIVE.THUS FAR I HAVE HAD ONE (1)REQUEST. I WOULD LIKE YOIUR OLD ONE BACK TO INSPECT IT PLEASE

THANK YOU

FRED KANTER

The Moraine power brake unit on those old Buicks do look like something of a knock-off of the Bendix TreadleVac - at least from outward appearances.

It was the Moraine unit used on '53 Buicks that got blasted in Nader's book, "Unsafe at Any Speed" for a design issue that resulted in an unexpected, catastrophic loss of braking action (yet which has no counterpart to the BTV). I suspect that Buick kept changing suppliers as GM-Moraine tried to work the bugs out their design.

Quote:

I'd guess ol' Ralph never talked to many Packard owners. He had it out for GM, after all.

Craig

During the time Nader wrote his book, the mid-60's, we were very involved in the Packard business and were driving BTV equipped cars as daily drivers. We were not aware of any unusual failure problem with BTV's on Packards or any of the muitiple other makes using BTV's

In this forum there was a report of the relatively quick failure of a unit twice after rebuild. This was not common to my knowledge on units rebuilt in the 60's or on the units we rebuilt on our own cars.

I suspect that Nader did not report on BTV Packard failures or on the numerous other makes because they were not failing at an unusual rate. Keep in mind that manual master cylinders have been failing since the late 20's when they were introduced, again not at an unusual rate.

I have been puzzling over BTV failures for quite a while and I have a question.
If the vacuum piston does not retract all the way to the top of the canister, is there still a path for vacuum to exert some force against the master cylinder and pull a steady though small vacuum against the master cylinder? Could this steady vacuum on a high speed continuous run slowly extract brake fluid from the master? Does the poppet valve close the vacuum path even when the vacuum piston is not all the way to the top of the vacuum canister? I hope I have stated my question adequately for all to understand.