1961 brake bleed issue

[Sargent_Arthur]

I've been having brake issues since I bought the car almost two years ago. I have since converted to disc. I have been bleeding with my pneumatic bleeder and got all wheels to bleed fluid with zero air bubbles. My brakes still are failing and I do not have much experience with older brake systems. Any help? The previous owner replaced the master cylinder. I don't see any obvious leaks in the system.

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[AlphaWray]

Failing how? Pedal immediate bottoms out? Pedal starts soft but pumps up with a few pumps? Pedal starts fairly strong but then the pedal slowly bleeds to the floor while holding pressure?

 

[Sargent_Arthur]

When the car is totally off no power from the ignition the brakes will go to the floor with very little resistance. When the car is running they feel very spongy and will not stop the car.

 

[74 Harley]

Replace the master cylinder!

 

[AlphaWray]

Agree. Replace the master cylinder. Don’t just do a kit. (If they even sell such a thing this days.) Piston in the master cylinder has a couple of o-rings and rubber flange rings. Those wear out and let fluid past them. It’s like the piston is just floating in a tube of brake fluid. When those rubber parts wear down far enough then the metal piston scars the wall of the cylinder. Which, if you just replace the rubber parts, that scarred rough metal surface inside the cylinder will chew up any new rubber parts leaving them useless in about 30 seconds.

Yes, my granddaughter says the same thing. “Pop pop, you don’t need to explain everything. You take too long for an answer.”

 

[Sargent_Arthur]

Agree. Replace the master cylinder. Don’t just do a kit. (If they even sell such a thing this days.) Piston in the master cylinder has a couple of o-rings and rubber flange rings. Those wear out and let fluid past them. It’s like the piston is just floating in a tube of brake fluid. When those rubber parts wear down far enough then the metal piston scars the wall of the cylinder. Which, if you just replace the rubber parts, that scarred rough metal surface inside the cylinder will chew up any new rubber parts leaving them useless in about 30 seconds.

Yes, my granddaughter says the same thing. “Pop pop, you don’t need to explain everything. You take too long for an answer.”

I need the long answers. You answers help me make crucial decisions about this car. I'm used to working on newer cars where it's plug and play. They became boring so I bought this Tbird and it's sent me on a roller coaster ride. Thanks for the amazing help yall rock!

 

[AlphaWray]

Your blue ‘61 rocks! Nice choice for a “not a plug-n-play” car.