Triumph Repair: Brake pressure leakage, vacuum booster, flex line

Question
Soory Jin the car is a 76 TR-6. The master cylinder had been replaced also not too long ago (new).
Once again I get a brake pedal pressure loss forcing me to pump the pedal to re-establish brakes. Witht the engine not running the loss is minimal.

Answer
Mike,
If the pedal goes to the floor slowly as you push on it and you can pump it up again and if you keep doing this and don't loose any fluid, you have a bad master cylinder. If you loose fluid as you do this and have to keep putting in fluid then you have a leak somewhere and need to look at each caliper on the front and each drum on the rear and look at each flex line to locate the leak. If you don't see any leak anywhere and you are loosing fluid, remove the master cylinder and check to see if it is going into the vacuum booster. In which case the master cylinder is bad because it is leaking.
The pedal going down more when you run the engine just means the booster is helping you push harder on the fluid. BE SURE TO ONLY USE DOT 4 FLUID!!!! IF YOU PUT IN DOT 3 YOU MUST FLUSH IT OUT COMPLETELY AT ALL FOUR WHEELS WITH DOT 4. DOT 3 WILL MELT THE SEALS!!!!
Let me know what you find.
Howard