Hi, after changing all brake lines and brake hose (in any case it was due) , do I need to bench bleed the master cylinder again ?
Did that to solve my hard brake pedal, after checking booster, vacuum and combo valve etc.... If I bench bleed, is there anyway I can see or feel
that new master is good or not and could have cause that hard pedal ?

71 442 power disk brake.

Thanks a lot, hope to solve this soon.

 

If the MC was emptied completely, I like to bench bleed again due to the mounting angle causing an air pocket. A hard brake pedal is caused by a bad booster or no vacuum.

 

I'd bleed the MC again if the whole system was disassembled.

 

Thanks, booster is new and vacuum is good, I did a test with vacuum hose attached to booster and disconnected, big difference in hardness of the pedal, so that's why I think the booster and vacuum is good. Anyway I'll do some test
again after bleeding.
Thank you oldcutlass.

 

I will thanks, and is there any sign I could see if that master is not working properly ?

 

To test the vacuum booster depress the brake pedal to the floor. Start the engine and the vacuum booster will pull the brake pedal closer to the floor if it's good.

Here's a handy kit to bleed the master cylinder. If you're able to bench bleed all the air out of the master cylinder it's good.

https://www.oreillyauto.com/detail/c...der/mtm0/14151

 

Yes I'm using this kit, and test again Booster after bleeding..