Master cylinder, reverse bleed

[Denisefwd93]

Need to replace the booster, master cylinder doesn't seem to leak but I'm thinking "replace it anyhow" I've been through this on many vehicles throughout my lifetime. we always bench bleed them, that's a given.

But, I was thinking, I know that's dangerous lol, When you put the new master cylinder in place the only air would be between the lines and master cylinder it just seems silly to bleed it all the way down from the wheels, when you should be able to push fluid up from the wheel cylinders just to get those couple bubbles out of master cylinder. Anyone done this?

 

[RonD]

You can

Get two clear plastic hoses that fit on one front wheel and one rear wheel bleeder, you need to open the bleeder so leave nut part open to get a wrench on it.

Two cans or containers of brake fluid, at hood or bed top height, higher than the Masters lines, I used duct tape rolls to keep cans from tipping over
Start siphon on each then put hose on bleeder.
When you are ready to install the Master, open each bleeder and fluid should start to flow slowly out of the brake lines at the Master end.

You can do this one line at a time as well, so do the front then do the rear

 

[adsm08]

Or you can do what I have always done.

Bench bleed the new master, install it, and then just bleed it right there at the master. Crack both lines, push pedal down slow, and close them while the pedal is going down. Only takes two or three shots most times, and I've never had a problem from it.

 

[Denisefwd93]

Thank you! I also have a mityvac.

today's project was replacing the radio, got to have my Bluetooth you know.

I found out the rear speakers are not working but they were not working with the original radio either so some further investigation into is need, but for now I have a radio that works with a cell phone.

ADSM, the way you do it makes a lot of sense!

I did pick up the master cylinder today with the booster.

 

[adsm08]

ADSM, the way you do it makes a lot of sense!

That was taught to me originally by an old-timer who drank beer like it was more important than water, and I never trusted it until years later when I got my first dealership job and one of the senior techs there had me do it that way. At that point I figured it must work.

Over the years I learned that a lot of guys do that, or some variation on it, to keep air from an upstream repair from getting into the ABS unit because the ABS service bleed function isn't always reliable.