Do you know if A/C has something to do with the brake system? First of all, my A/C sometimes work and sometimes not. When working, the idle rpm is normal and freezing cold. When it is not working, it produces zero cold air and the rpm jumps to 1500 rpm. It works like 10 minutes then quit working for 5 minutes then come back on. This doesn't concern me too much but one big problem is when it is not working properly, my brake pedal got affected and sinked to almost the floor when I try to brake. When the A/C resumes working, the pedal will return to normal and feel super solid immediately. It shouldn't be the master cylinder because I just put a new one in it and bleeded the brake. Does the A/C system created a vaccum leak to the brake system(brake booster) or something? I just don't understand.......?! Please advice. Thanks

 

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it shouldn't affect the brakes. i would check the calipers and lines for leaks. the vaccum leak does make sense since the a/c does draw power from the engine (notice the rpm's drop whne it's turned on). i would think about changing the booster.

 

if the booster was going bad you would have a hard pedal (no assist) not the sinking pedal symptom.. the a/c system and the brakes have nothing to do with each other not even in the vacuum sense.. i would make sure you tightened up the lines goin to the Master Cylinder and then bleed the brakes again in the proper order your A/C concern could be a number of things, sounds like you could hav a leak somewhere