Brake Bleeding problems

"Joel" wrote: (1984 Ranger)

I'm trying to bleed the brakes, each time my helper pumps them I get additional air through the line on the right rear brake. Does the master cylinder need to be replaced? ______________________________________

Are you closing the bleed valve before letting the helper release the brake? If the valve is left open, air can be drawn back into the line when the brake is released.

Is the fluid reservoir full? During brake bleeding, the reservoir must be repeatedly refilled with fluid or it will run dry and draw in air. This will force more air into the brake line being bled.

Are all of the other line connections tight? Air could also be drawn into the master cylinder from a loose line connection to another wheel or another line being cracked, or another wheel bleed valve being left open.

Good luck.

Rodan.

Since each piston of a dual master cylinder supplies two wheels, and you only see bubbles at one wheel, I would suspect that you are just not getting the air out of that one.

Some dual master cylinders are known for being hard to purge totally, but it is possible to do it without the aid of pressure bleeders if you are using the right technique.

When you get the system bled as well as you can, and pump up the master cylinder and hold pressure on it, what happens? If it holds the pressure, then that usually indicates a good master cylinder. If it pumps up, but holds only for a short time and then the pedal moves toward the floor, that usually means the MC is a goner.

Is it possible you have another break in the line somewhere? My race car was doing the same thing and we found another break in the hardline going back to the master cylinder.

If the brakes were fine before, I'd go on the assumption that the problem is air getting in somehow either through another break in the line or air still trapped in the line going to the other wheel. (for example if a bleeder screw was left open)

Ray

Thanks for all of the input, I think that the possibility of pumping air back into the system is what is happening, I get a solid pedal when all bleeders are closed and the breaks are pumped up. I'll check the rest of the lines and look for any leaks, I don't think that it is the case. I started the project out with pump... hold... bleed... lock down... pump hold bleed... lock down.... I got impatient and read the back of the brake bleeder package... which stated.. "pump until the there are no more air bubles - don't let the MC run dry... "... So I changed tactics... and one wheel worked perfect... the other did not. I'll go back to my old method and let you know how it went.

Thank you for the input! Greatly appreciated.

Joel

Get some windshield washer tubing, or better yet, some clear tubing about the same size, push that over the bleeder screw and let it dangle in a 20oz. soda bottle (or other similar container) while bleeding. Not only does that keep the brake fluid from running down your nice, freshly painted suspension parts but also it will remove any possibility of sucking air back into the wheel cylinder on the upstroke, save for around the bleeder threads. Thus you can omit tightening down the bleeder screw for all but the last few pumps.

good luck,

nate

=3D=3D=3D=3D=3D=3D=3D =3D=3D=3D=3D=3D=3D=3D "IF"......ALL.....the other wheels are bleeding out good, no air....then.... you CAN isolate the problem to the RR Braking system. (From where the line starts to cylinder)

Now.... IF the line..AND...its connections are good... then...

air is still in that section of the system (very doubtfull)

the bleeder is not seating (possible, but doubtfull)

the cylinder is sucking the air in. (very likely)

the rear brakes are not adjusted up. (very likely)

Facts,not fiction. (based on the facts you posted)

anywhooo..... Before you go pulling your hair out, make SURE the rear brakes ARE adjusted correctly or you will spend wasted hours trying to figure out why they won't bleed out.

again, Fact, not fiction

Logic would lend to the fact, that if the master cyl. was allowing air to one wheel, it would allow air to another.

Logic would lend to the fact, that air in ONLY one wheel can be isolated to that section by eliminating the components one at a time.

the facts sir, jest the facts.

~:~ MarshMonster ~sips his crown n coke~ ~:~

Excellent information. I will follow-up with checking the adjustments on the rear breaks.

FYI... I found that the right front break line -> flex line was loose, this appears to be the largest problem.

Thank you all for your help. Great information and extremely helpful.