Packard Forum Index » V-8 (1955-56)

The hard pedal is not due to the compensator port. If the comp port was bad then the pedal would go to the floor with no effort.

Assuming the power unit IS connected to vacuum then the hard pedal is due to either the air filter in the power unit is plugged or the wheel cylinders are too small in diameter. BE sure that the wheel cylinders are 1-1/8 front and 1 inch rear. Picnched brake lines or bad hoses can cause it too.

Other possibility of hard pedal could be various internal malfunctions of the power unit. The air filter i mentioned above is the easiest to check.

The reason i'm beating on the wheel cylinder size is a rather long story related to a current 56 Packard brake project i have going on right now.

In every car I've ever owned that was equipped with (vacuum) power brakes, I could easily check for a lack of power assist from the driver's seat, as follows:

1) With the engine off, pump the brake pedal a few times to make sure the vacuum reserve is exhausted.

2) Release the pedal completely, then re-apply foot pressure and hold.

3) Start the engine. Vacuum will build quickly, and you should feel the pedal drop away a slighlty (under foot pressure). If not, then you have no power assist.

To find the cause, the first step is to remove the hose from the check valve at the back of the carb (with the engine running) and inspect for the presence of vacuum at the valve. Then, work your way upstream with inspection to the tee at the booster and the vacuum reservoir (tank).

If you can eliminate vacuum source and external leaks as the problem, then there must be an internal problem with the booster itself. Something may have been overlooked in the rebuild process, but check the air inlet filter on the booster to make sure it isn't clogged BEFORE you remove the thing and ship it back.

The Bendix TreadleVac (aka - BTV) is not nearly so complicated (or deadly) as some people make it out to be, but there are some parts that are not readily available to the public at-large - especially with the booster internals. Reputable rebuilders may have repro'd them, but will only sell them as part of their repair service.

Caveat - if you're wanting your unit rebuilt and returned, my advice is to stay away from "middlemen" who simply sell on an exchange basis, but deal directly with a competent rebuilder. (Hopefully, owners will share their favorable experiences by adding such suppliers to BigKev's Packard Directory.)

Interesting how we got from gas tanks to brakes. I've driven TreadleVac cars since the 60s with no failures. Many of my Packard friends have rebuilt units which are VERY sensitive, capable of launching their occupants out over the windshield (in a convertible). Mine on the other hand is rather insensitive and I occasionally find myself pushing rather hard. It was rebuilt by the best in the business, and replacing wheel cylinders and hoses did not make a difference. It is receiving ample vacuum and the vacuum system is tight. However, replacing the front brake linings made a very significant improvement.

I agree - properly serviced, the BTV performs just fine.

However, one really needs to go through ANY decades-old system with a fine tooth comb. In addition to sheer age, a lot of mickey-mouse repair work could have been done in the years since the dealer network evaporated.

You also have to be careful with substitute parts. For example, I received a brake overhaul kit with shoe return springs that were NOT colored the same as OE, and there was NO note included to explain the difference. Although I contacted the seller for clarification, I have to wonder how may people didn't go that far and might have installed the springs incorrectly. I've seen other cars with such springs installed incorrectly where that created a grabbing condition that was sufficient to lock the wheel - at speed.

Thanks to all of you for the very valuable information.
I had found the left front hose was plugged completely and the right rear hose was cracking so I replaced all of the hoses (which I bought from Kanter) and then was getting fluid to all four wheels during the bleeding process, which is a bear of a job to do by one person, even with the so called vacuum pump bleeder. As you know it is not hard physical work, it's just more difficult to get all of the air out of the lines when there is no one at the drivers seat.
I will follow all of the advice as suggested here and let you know what will hopefully be good results. One thing is for sure I should know how all of the various system works on a 56 Pat by the time I'm through, AND THAT IS A GOOD THING!

BD,
I too am experiencing hard pedal, with a rebuilt TV unit, so if you discover just what is causing the problem please post your results. I replaced all wheel cylinders and all hard and rubber lines. Before I was ready to bleed the brake system I ordered a set of Speed Bleeders and a fluid recovery bag from speedbleeder.com. This turned out to be the easiest brake bleed I have experienced and did it solo, was able to leave wife in the house.
Bill

Rowdy, Sure thing, I will post my findings here "soon I hope" and for your sake and mine I hope it is something very simple and easy to fix.
I'll check out the speedbleeders.com

BD,
You'll wonder how did we bleed brakes without them. If you contact them with car info they will give you valve number, the one for my 56 was SB3824.