1957 power brake response

[knuckle47]

1957 with power brakes…. Mom and dad were T-bird crazy with their 55 and sold it long before I got a drivers license 51 years ago. The car I have is a driver but looks so much nicer, clean. detailed and runs like a top. After my first 20 feet and I tested the brakes, wow… it felt like manual brakes and took a lot more effort than I would have believed for power brakes. Engine runs beautifully and my curiosity dictates investigating what would be normal operation for this assembly. This is my first vintage car but I have restored dozens of vintage motorcycles from the 20’s thru 60’s…they rarely had brakes (). I have the manuals and will start digging in …any thoughts on what may be a starting point. I have driven over r0 years with power brakes…this just doesn’t feel like it.

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[apines]

The first place I'd look is vacuum since that's what provides the power in power brakes. Be sure the vacuum line is properly connected and not cracked or otherwise leaking. After that, the diaphragm inside the booster is a common point of failure. Replacement diaphragms are readily available at the t-bird part suppliers.

 

[knuckle47]

The first place I'd look is vacuum since that's what provides the power in power brakes. Be sure the vacuum line is properly connected and not cracked or otherwise leaking. After that, the diaphragm inside the booster is a common point of failure. Replacement diaphragms are readily available at the t-bird part suppliers.

Sure enough… the tube running from the rear of the manifold to the rubber hose on the booster is severely crimped right at the 90 degree bend. Thanks !

 

[Ward 57]

Well that would certainly do it. I've got my booster out for re-building and while diagnosing whether it was working or not, the shop manual states that when holding down on the pedal it should drop a smidgeon when starting.
I've got an early '57 that has a rubber hose all the way from the manifold to the booster up and over the valve cover.

 

[knuckle47]

That is exactly what I had done to see whether or not there was a problem… after it started, nothing. After reading it, I remembered how some of my regular cars as I was growing up would do just that…I would always put my foot on the brake to start it and you would feel it move. Ordered a new tube just a few minutes ago

 

[knuckle47]

This is what mine looked like. Not sure if the angle shows the full bent area

 

[Ward 57]

It shows pretty well. It looks like it would be easy to disconnect at both ends and try blowing through it and see just how restricted it is. I know replacements are available.
I'll attach a couple of pics to show my configuration. I also had a 180 deg. bend at the manifold. whe the engine was replaced eons ago and it was a small shop so they just made things work as it was 'just an old car'. Dug through my old parts and found my original steel vacuum line that wrapped around the head and not over and connects to the side of the block on the manifold and the to the fuel pump vacuum line.
I had a local shop copy it and was able to let the hose breath. Sent my original to CASCO as a template for a factory configuration that is fairly rare.

 

[doug7740]

That is exactly what I had done to see whether or not there was a problem… after it started, nothing. After reading it, I remembered how some of my regular cars as I was growing up would do just that…I would always put my foot on the brake to start it and you would feel it move. Ordered a new tube just a few minutes ago

If you disconnect the hose at the brake booster and connect a vacuum gauge, you will be able to tell if the kink in the tube is the cause of your power brake response issue. With the engine running at idle, the gauge should read at least 17” of vacuum at the brake booster. If you find that there is sufficient enough vacuum at the booster, then it’s time to rebuild the booster.

Attached are the brake booster repair kit instructions incase you decide to rebuild the brake booster yourself. If you've restored motorcycles then rebuilding the brake booster shouldn't be any problem.

doug7740
1955 Thunderbird Blue

 

[knuckle47]

You guys have given me exactly what I need to EASILY move on…thank you. I was looking in the manual what vacuum should be there but hadn’t come across it yet. the weather in the northeast is getting cooler and aging has not been kind. Still waiting for the dream of a heated pole barn. As I dig into this, I know I’ll have some issues so i will thank you again in advance for you thoughts and suggestions

Sincerely appreciate the brake booster diagram and the photos

 

[knuckle47]

So it is still cold out but I went and measured the vacuum at the booster hose and despite that kinky bend at the manifold, the vacuum gauge is reading 18" So it seems at this point to indicate the booster needs a rebuild. Ordered the kit today

 

[Frankie the Fink]

The classic 3 test of early brake boosters on basically any American car:
1. Does the valve on the booster act only one - way ? Blowing/sucking through it should confirm this.
2. Pumping the brake with the car engine off depletes the vacuum reserver and then pressing the pedal again, firmly, while starting the engine should cause the pedal to dpress an additional 1" or so as the booster vacuum is built up.
3. The vacuum reserve is tested by turning the car off and pressing the brake pedal several times, you should still get a "boosted" pedal before it becomes firm as the vacuum reserve is depleted.

 

[knuckle47]

Frankie the Fink… we failed all three. The Blowing / sucking seems to allow some movement but very tight and not like it spring back from either action. Number 2 and 3 are more definitive and they totally failed. Glad the parts are on their way