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Strange brake issue - firm pedal collapses
Car is a 1968 912 with 911SC front calipers, 912 rears and a 19mm dual-circuit master cylinder.
I have just fitted a new (ATE) master cylinder as I suspected the old one was failing. The system has been bled multiple times - I’ve put perhaps a gallon of fluid through the lines!
I can get a very good, firm brake pedal, which holds. However, if I release pressure just a touch, the pedal slowly collapses (although it never reaches the floor).
The way this translates in driving the car is that the brake pedal has initial normal, firm feel, but after three seconds or so it slowly gives way.
I’m absolutely stumped - have never experienced anything like this, and I can’t visualize what’s happened here.
Would love to hear from anyone with previous experience of this issue!
James
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