New Master cylinder, trouble bleeding

[TDW]

I just replaced the brake master cylinder, and did a bench bleed. Now when I try to bleed the lines, the farthest brake will not bleed.

I tried a vacuum pump and also just pumping it. I'm assuming I've got air in the system somewhere.

How do I purge the lines and get the brakes bled correctly?

 

[GOOSE]

Maybe the bleeder is clogged? Try to leave bleeder open for a few hours and see if gravity may help you.

 

[OLDBULL8]

Looks like you bought that Van that was on Craigslist in Portland. Is that the one you are working on?

When you bench bleed the MC, read the directions carefully. There is a certain length of stroke, and do it slowly, that is important. You may have to bench bleed several times to get the trapped air out. Sounds like that's the problem. It's more difficult to do when you have a 2 compartment MC. Takes two people to bleed the lines, apply brake pressure, open bleed valve, pedal to the floor,hold there, close valve, let up on pedal, do it like that until no more air is seen. Use a clear tubing into a jar with a little fluid in it so you can see when all the air is out. If you can't get any fluid out at the rear, it's possible that the hose to that brake is collapsed inside, or the valve is plugged with dirt/rust, take the valve all the way out and make sure it's open. If the brake fluid is old and brown keep bleeding the lines until clear fluid comes out. Just make sure you keep the MC full of fluid or you have to start all over again. Takes normally a quart to flush the system.

 

[MIDNIGHT RIDER]

I quit that bench-bleeding foolishness years ago; also, I seldom ever resort to the "okay---hold'em" method either .


Mount all the new components.

Open ALL the bleeders at the wheels.

Fill the master-cylinder to the brim; leave the cap off, and walk away.

After maybe half-an-hour, re-fill the master and close all but the closest bleeder.

Give it another spell; close that bleeder and open the next farthest one, etc. and so forth.


Be sure and not let the master drain low enough to expose it's valve-holes.

This method works far better for me than "doing it by the book".

 

[TDW]

Looks like you bought that Van that was on Craigslist in Portland. Is that the one you are working on?

Yes it is the one in Portland. Running strong so far, but who knows what I might run into during this process.

I did check the bleeder valve, and it passes air. I was thinking of disconnecting the lines from the master, and vacuum pumping all existing fluid out, and then refilling the lines by putting the front end of the line inside a clean jar with fresh fluid. I like the fill and wait idea too.

Thanks for the ideas, I'll give it a try tomorrow morning. It's supposed to be nice outside, and it's my day off. Better than trying to rush through the job before the sun goes down.