Packard Forum Index » V-8 (1955-56)

If you have power brakes and good vacuum but a hard pedal one thing a couple of people have found is the flex hose inside the vacuum can connecting the source to the piston has come off the metal nipple at one end. It's just a slip on fit with no clamps so can easily come loose if conditions are right.

Howard:

Being somewhat mechanically challenged, do you have a picture of that so I have a reference point to look for.

ALK

I think ford uses the same sending unit. for sr.

Quote:

Couple of threads on site from last year or year before with some real pictures of the hose if you want to search. In the meantime if you look in 55-6 service manual, page 9 of brake section, there are several illustrations showing the hose and how it attaches.

For some it has slipped off the entrance nipple on inside of can. Maybe due to age since it has to flex at that point or was tired because that connection is removed any time service is done on the unit. Don't remember if there were any other symptoms such as a racing engine or low vacuum or hissing indications but the common theme was hard pedal with no boost at all.

If you don't find any other reasons such as leaks or a stuck vacuum check valve or even hydraulic issues, maybe worth opening the can to look at the hose.

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ECH OP6091 from Napa is the oil gauge sender for senior cars. Some Ford products. When Jim bought one last year to test it was around $15.

Well I've got all the bolts out that hold the t-vac unit to the floor. Problem now is that the brake fluid line nuts seem to be frozen onto the end of the master cylinder. Going to get penetrating oil and WD-40 to try and loosen them up. I've got and old unit that has the back plate off and I can now see how the thing goes together. Once I can get the backing plate off on the car unit I can see if there are any leaks. Will heating up the nuts with a propane torch cause
any damage.

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Probably.

However, you DO NOT have to remove the Treadle-Vac unit from the car just to check the vacuum hose that HH56 mentioned.

If you FIRST remove the four bolts loose that hold the toe plate to the treadle-vac and THEN the bolts that fasten the toe plate to the floor, you can remove the just the toe plate to access the end plate, with the unit still in-car.

This internal vacuum hose was made of a very pliable rubber that's not reinforced, but formed/molded to fit within the confines of the vacuum shell, while permiting full travel of the vacuum piston assembly. No clamps should be required for this hose; otherwise, it needs to be replaced. Be forewarned that fuel hose is NFG in this application.

Meanwhile, have you verified the external vacuum supply? For example, I've seen more than one case where the check valve failed (even on modern cars), resulting in hard pedal and loss of power assist. However, the valve on these cars is located at the the back of the carb; hopefully it was removed before the carb was "tanked" for rebuild.

If not a vacuum problem, then could be something internal the to master cylinder - on the hydraulic side, which will require removal of the unit from the car.

BTW, I've found it easier to R&I the unit with the line to the front still attached. That is, disconnect that line at the tee on top of the frame rail. Then, just before you go to reinstall the unit to the floor board, run the tube nut at the banjo fitting finger tight; give it a final tightening AFTER the other end is reconnected to the frame tee.

Brian:

I am not sure that will work. I have the big floor plate completely off and the 4 retaining bolts out. There are 4 tabs that are bent over that seem to hold the backing plate to the main part of the T-V.

Al

There's enough room in-car to bend those four tabs open to a 90-degree angle. Believe me, I've done it more than once, but you have to be flexible in your approach.

IIRC, I started out with a small pocket screwdriver (the ones that are often given away as advertising) and as things opened up, I worked my way through stouter prying tools, but might have finished with a pair of pliers.

And since you're going to the trouble to look at the hose, go a step farther and remove the screw holding the input nipple assy and breather cover to the can and remove those as well. Once the obstructions are out of the way pull the power piston straight out and see what kind of mess is inside. If like many there will be a good chance brake fluid has been sucked inside and congealed. If you find some verify the relief port gasket and the seals. If it's been a long sitting unit it may well need a rebuild --