Packard Forum Index » V-8 (1955-56)

Problem is nothing will fit in that space without some compromise. The firewall units are designed to work with more pedal leverage than the 1:1 on the present setup. Anything requires either relocating higher on dash and/or to the side and modifying the pedal in some way. With the steering column where it is, there aren't too many options without seriously modifying something.

HH 56 Thanks for the pictures, Yes I tried pulling the pedal back (I had a friend who had a string tied to the brake pedal..another story). Come to think of it strangely the symptoms are the same even before we redid the master cylinder, right down to the brake lights.

HH 56 The space is tight and modifications could cause even more trouble. If you are correct about the compensating valve, perhaps pulling the master and flushing the lines could help. Could the residual pressure check valve be sticking as well?

There are a few who will dissagree, but the Bendix TreadleVac performed well on many millions of cars including Packard, Lincoln, Mercury and several GM makes and is a good unit for it's vintage. But I'd be VERY leery of a "local" rebuild, it simply isn't worth the risk with brakes to not go to a TreadleVac professional. Highly recommended is Ed Strain in Florida, you'll find his advertisement in the Packard section of Hemmings.

A flush certainly wouldn't hurt but unless you found chunks of sediment on your rebuild, probably wouldn't help either.

The residual valve is designed to keep 5-10psi in cylinders so rubber cups stay flat to pistons and lips against cylinder wall. Only thing I could see failing is if the rubber has been contaminated with petroleum product and is swelling with heat or the retainer has been smashed down and totally blocking the outlet. Would think there would be some indication when applying brakes that something was wrong if that the cause. Easy enough to remove the fitting and pull it out to check condition--unfortunately not something to be done on the fly and means bleeding brakes again.

Brian mentioned the vacuum portion. There are any number of things that could go wrong there. Another easy thing to do when fails is to pull off the vacuum line to brake. With no vacuum, that would eliminate that part and the pedal would be free to move if the vacuum were partially applying. Of course, something could also be jamming the power piston such as fluid which has leaked in, corrosion or mechanical damage. As I recall, there is not much clearance between the power piston and the plate covering the cylinder end under the toe board. Any chance something has gotten into the opening and preventing full travel. At any rate, sure sounds like something needs to be professionally gone thru.

The brake fluid was full of gunk and perhaps some got back in the cylinder. We shall see. thanks for all of your input.

Lets do the ez things forst. The filler plug of the master cylinder hhas a square on it for a wrench. On one side of the square there is a VENT HOLE.

At the TOP of the vacuum unit near the fire wall there is a VENT WITH filter in it. THIS vent must not tbe restricted.

Morgan,
I have been following this thread because I experienced some of the same things you have after the purchase of my 56 Exec. I experienced hard brake pedal and binding rear brakes, would not release pressure to rear. I called Ed Strain and he suggested I flush lines and replace all rubber lines first. I replaced ALL lines and flushed master, this resolved the binding problem but not hard brake pedal, this took a rebuild by Mr. Strain and now brakes work fine for a 56 vintage automobile.
Rowdy

ps:Am in process of upgrading to front disc set-up.

This is a common problem after replacing the master cylinder on many cars. Caused by not enough clearance between the pedal rod and the master cylinder, and the piston not retracting all the way.

There should be a certain free play on the pedal, if not you will have this problem.

Morgan -

The repro overhaul kit for these master cylinders, like the original from Bendix, would have everything you needed to "refresh" the hydraulic section - EXCEPT for the compensator port valve spring. However, I doubt that spring is a problem in this particular case.

I suggest you first visually verify proper movement/operation of the compensator port valve stem, as noted by HH56. If that checks out, then try his later suggestion about disconnecting the vacuum source when the problem occurs. You should be able to easily access the large supply hose for the power brake unit on the check valve located at the rear of the carburetor throttle body - originally secured by a spring wire clamp (which makes for easy removal).

While there are undercar power brake units available in the kustom aftermarket that can replace the non-power brake master cylinder that was mounted under the floorboard on 1954 and earlier Packards, you will not have sufficient clearance to use them on the V8 models. While I tip my hat to a couple of other members here who have adapted other dual-chambered units, there is no alternate power brake unit I would recommend for the V8 Packards.

Yet, don't believe all the negative hype about the Treadle-Vac. Properly serviced it works fine on each of my cars (and I went through them myself). Should you need the service of a professional rebuilder, just be sure to send it to a reputable Treadle-Vac specialist. Do NOT send it off to someone who is merely expert at rebuilding and sleeving conventional master and wheel cylinders.