regnevazota

Ok, so I put on a new MC, bleed the system and the pedal is nice and hard -- way better than with the marginal MC. But then I see this tiny little bubble of DOT fluid right where the hose goes into the last metal crimp at the caliper. As the pedal kept being pumped it would get progressively mushier. Obviously air was getting in at the hose/metal crimp. Didn't see any other leaks after checking all the metal lines and hoses. So, I replace the bad hose and bled that line again (local techs telling me I do not have to bleed the entire system again). I didn't but then an ATE engineer tells me the air has probably gone back into the MC, that if it wasn't trapped that is where it must go, has no choice, simple physics. Seems logical. But if that is true, then why does it have to stay at the MC? I mean once it worked its way back to the MC, does it stay there or can part of it go into the other port/line, ergo, cause mushiness???

95whitehatch

When you bled the system, did you bench bleed the master cylinder?

regnevazota

Are you asking me if I bled the MC off of the vehicle before reinstalling it? I did that time, that's why I suspect the air in the lower part of the system has migrated back into the MC.

But I don't do it that way anymore -- too messy and not necessary. Its easier to do it on the vehicle. Bench bleeding is kind of a procedural buzz word now for bleeding the MC after it has been removed and/or replaced on a vehicle. I gotta say that this brake bleeding topic has been discussed so many times on the Internet and so many have discussed it, it is unbelievable how much. I read of so many people asking what the cause of their problem could be, why it didn't work, essentially why the pedal isn't as tight as they want it to be. And yes, they are asking that question long after a successful bench bleed. Every forum for every brand of vehicle.