56 TBird Power brake inop

[Jim G]

Well— Still working on getting my 56 TBird drive running safe! Engine started idling a bit rough on and off and idle too low after a drive! Stared when brakes have lost power assist and brakes dragging a bit after a stop. If I hit the brake pedal 2-3 times brakes release and roll freely again. Brakes don’t completely lock up as can power up but rolls like holding on a bit of brake pedal sometimes. I have also been fighting my brake lights staying on. I replaced two brake light pressure switches - each one more expensive type. If I tap the brake pedal a couple times the brake lights go out! Takes hard push on pedal to come to stop. Vacuum line from intake manifold is new and connected to to power booster. Hasn’t worked the best since I bought it but did appear to have some power assist. I’ve bleed the brakes at the wheel cylinders but did not bleed the fitting on the power booster..?? Think’n a overhaul exchange power booster coming up? All thoughts welcome. Jim G

[Alan H. Tast]

Have you replaced the flex hoses to the front wheels and the to the rear axle. What you described looks like symptoms of the hoses failing from the inside.

[Jim G]

I have not replaced the hoses. Would not have thought that would act like this to loose power assist brake. Maybe hoses are cheaper than a booster overhaul to try for the fix. Suppose there is a way to isolate lines or front and back? Jim G.

[Daddio]

Rough idle and loss of power brakes at the same time could be due to a loss of/leaky vacuum. Be sure to check your booster to engine connections/hose again and see if the booster can hold a vacuum with a hand held pump.

[Alan H. Tast]

I have not replaced the hoses. Would not have thought that would act like this to loose power assist brake. Maybe hoses are cheaper than a booster overhaul to try for the fix. Suppose there is a way to isolate lines or front and back? Jim G.

One of the classic signs of brake hoses failing is brakes failing to release after being applied. The interior of the hose can deteriroate and swell to the point that it acts like a one-way valve and not allowing fluid to return to the master cylinder. Even if the hoses look OK on the outside, on the inside they could be trash. I strongly suggest replacing all the flex hoses if they haven't been changed out yet. As for isolating front vs rear, don't cheap out and only replace the fronts and not the rear, and vise versa.

If you REALLY want to isolate the fronts from the rear, that's what a dual master cylinder conversion will allow you to do.

[Jim G]

Ok— hose change set it will be! Have you ever bleed the power booster at the bleed point on the booster? And how would I check the booster to see if it’s working? Check a vacuum holding on it?? How? Jim G

[mike3121]

Sounds like your Power vacuum booster isn't working. I have the same problem with my recently purchased 57. It sat for a long time and the brake fluid turned to jelly. If it's a brake hose you'd be getting brake fluid dripping on your garage floor. On my car it was determined to be the brake booster, it's letting air into the line so the front brakes are mushy. I have to pump the brakes hard when I go to stop. The problem with these boosters is that they have to be sent away (MAC's is the cheapest) to be rebuilt and it takes 4 to 5 weeks. No shop is going to allow your car to sit around that long so you'll have an expensive tow back and fourth. As far as I know no one makes an "off the shelf" replacement. Good luck.

[Joe Johnston]

White Post Restorations rebuilt my booster, including boring and installing a sleeve in the inside to fix the pitting. Was less than a 2 week turn around. They provide a warranty and easy to remove and ship to them. Google will find their contact info.

FIRST I would replace the 3 rubber hoses as Alan suggested, then completely flush and bleed the system. Its common for these hoses to fail internally and show no evidence on the outside. Start simple but be methodical and complete in diagnosing the repair. The entire system will then need flushed and system bled including the booster. Studying the Shop Manual may give some useful info.

Keep in mind, these remote Midland boosters will not provide the amount of boost we have become accustomed to in our modern vehicles.

[BuddyP]

White Post Restorations has an excellent reputation.

[Donnervogel567]

When bleeding brakes with a vacuum booster, the booster should be bled first, then the wheel cylinders. Also,
with a failing brake booster check the master cylinder brake fluid level regularly, as brake fluid can leak internally
and is not visible externally. Generally, brake fluid can accumulate in the vacuum chamber. The only way to check if
this is happening is to loosen the the "clamp ring" and crack open the two halves of the vacuum chamber.
Before doing this place some rags to absorb any fluid that may drain out.
Bob H

[Donnervogel567]

One of the most overlooked flex hose in the T-Bird and the one of the most difficult to replace is flex hose over the rear axle.
Bob H.

[seany-boy]

+1 for White Post Restoration

Take the vacuum line off the booster and block it then try the vehicle as the booster should be almost inoperative. The brakes will be noticeably worse and braking effort much more. You will know immediately if the booster is working at all.