Need to replace my MC. Got a new one, with the bleeders. Do you guys bench bleed this type with hooking up tubes to the line feeds, or put it in the car and then bleed it through the MC bleeders?

 

I bench bled the last one that I did about 6 years ago.

 

Bench bleed

 

Good to bench bleed because you can go through the entire stroke, and you can also watch for bubbles. On-car, you might not be able to get it to the end, leaving some air in the system.

 

If you try bench bleeding it on the car, I doubt you will ever get all the air out due to the angle it is on the car. I guess that is why they call it bench bleeding.

 

Definitely bench bleed. Last one I did was a couple summers ago and they included two port plugs with instructions stating that this was the preferred method nowadays. You level the MC (crucial) on your workbench, install the plugs, fill the bowls and push in and release on the plunger until no more bubbles. I questioned this method thinking the tubes were necessary...but, it worked great for me.

 

I guess my question, should have been, what are the bleeders on the MC for, or when to be used, if not when installing? I do bench bleed them, just wondering, when they were used?

 

Bench bleeding? Depends whose instructions you want to follow. I recently bought a Raybestos reproduction 1960s master cylinder and it's instructions recommended 3 different methods of bench bleeding. I pulled a Cardone master out of the box and it said that you should not bench bleed, and that you should pressure bleed instead.

I'll be the oddball who says that I have never bench bled a master, and that I never have a problem by not doing it. but that's only because I use a positive pressure bleeding system... one of those things with the big pot reservoir and pressure lines that go to the master.

Bench bleeding isn't necessary if you have a pressurized brake bleeding system. With a system like that, you just fill the master, pressurize the system, manipulate the pushrod and blow all of the bubbles downstream to the bleeder screws.

OTOH if you don't have a pressure bleeding system, bench bleeding is definitely going to help.

To answer your revised question -- I think that the bleeders on the MC are there to assist in bleeding air out of the lines without blowing it downstream. I think they'd be helpful if you're gravity bleeding a system, which doesn't provide enough force or flow to clear all of the air out of the lines. With a gravity bleed, an opening at the top of the system might be helpful for getting the air out. Personally, I like to just use high volume, consistent flow to get the air out.