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Discussion Starter · #1 ·
I am stumped. I have a 65 Giulia 1600 Spider with Disc Brakes. I was pulling the car out of storage this summer and the brake pedal goes to the floor - all slave cylinders were rebuilt within the last 5 years w/all new rubber hoses. No fluid on the ground or on any wheel.

Master Cylinder seems to be the culprit. Rebuild MC with new seals from International and using a combination of Air Compressor Bleeder and old fashioned pump and turn method I am getting a steady stream of fluid out of the speed bleeders.

The problem - when I first pump the brake pedal with all bleeders tight, I get some initial resistance and pressure but the second pump the pedal goes right to the floor and thereafter is limp. While bleeding it is the same thing. I can suck fluid using the air compressor to the bleeders but then when I use a pump and turn method I get a good stream out of the bleeder but then I tighten the bleeder and then loosen for a second pump and get nothing but air, no fluid at all.

I suspect that I have somehow screwed up the rebuild of the MC as the MC seems to be pumping fluid with the first pedal application but then it sucks air into it or is not refilling for some reason. The fluid level goes down while bleeding so there is a path for fluid but why would the MC only create pressure on first pump. Have I not tightened the large end nut down enough and air is being sucked in?

Any help is appreciated for this newby!
 

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If air was coming in there I'd think fluid would be leaking out, especially under pressure. Sounds like maybe an internal problem, that you're losing pressure internally? And no leakage past the small seal, into the pushrod boot on the MC, toward the pedal end?

Andrew
 

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I am not certain from what you say, which MC you have, but I had a similar but not identical problem which was caused by the push rod being too long and holding the piston in a position which restricted the flow of new fluid into the cylinder and thus allowing air round piston seal. Easily cured by screwing the push rod into the yoke until there is just a small amount of free play. Good luck.
 

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Discussion Starter · #4 ·
That is a good thought. I have adjusted the push rod to have the recommended 1.5mm of free play but perhaps I have erred on the conservative side and allowed too much free play.
 

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Discussion Starter · #5 ·
There is no fluid on the ground but I will take the heat shield off today and see if any fluid has accumulated in the rubber boot. Thanks for the help.
 

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Discussion Starter · #6 ·
I am back and have removed the pedal box from the car and have reassembled the Master Cylinder just to make sure I had it together correctly. Now that I am pushing the break pedal with my hand I can now feel that the plunger inside the master cylinder is being pushed but it is not springing back. I placed the long spring back in the cylinder of course. I did not hone the ID of the cylinder just cleaned it up as it looked perfect. Does the spring provide the necessary force to push the plunger back or is the pressure that is supposed to do it?
Do I need a new spring or have I not assembled the MC correctly? Do I need to put teflon tape or something on the end piece?
Any thoughts?
 

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Discussion Starter · #7 ·
All is well. I think I have correctly diagnosed the problem with the help of a local Alfa Guru. I took everything back apart and actually honed the ID of the cylinder. My (farmer) brother-in-law had cleaned it up with a wire brush and left it with too many scratches. Once I honed it, I lubed the heck out of everything with silicone brake lube and reassembled and it is working well now. I have the hardest pedal I have ever had and the car is stopping well. Thanks to all who wrote.
Now does anyone know how to diagnose and repair my horns?
 
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