Brake fluid replacement problems

[namari]

Tried replacing my brake fluid for winterization today. Opened the fluid cylinder reservoir, removed seal, attached drain hose, loosened bleeder valve and pumped brake until empty. Closed bleeder valve, filled up cylinder reservoir with new DOT 4, closed it up. Tried bleeding the air out of the line, but pressure will not build up no matter how much I pump. I pump, hold down brake, open bleeder valve (some new fluid flows out), close bleeder, pump some more, etc. Can't get pressure to build. What do I need to do? What am I doing wrong? Help please! Thanks!

[blaine]

Originally Posted by namari

Tried replacing my brake fluid for winterization today. Opened the fluid cylinder reservoir, removed seal, attached drain hose, loosened bleeder valve and pumped brake until empty. Closed bleeder valve, filled up cylinder reservoir with new DOT 4, closed it up. Tried bleeding the air out of the line, but pressure will not build up no matter how much I pump. I pump, hold down brake, open bleeder valve (some new fluid flows out), close bleeder, pump some more, etc. Can't get pressure to build. What do I need to do? What am I doing wrong? Help please! Thanks!

Your mistake was to empty the MC.You should add fluid & bleed till fresh fluid flows out,never emptying the M.C. Try filling the M.C. with fresh fluid & Bleed at the M.C. by slowly cracking the line open.Have a rag wrapped around the fitting & line to capture any fluid coming out as it will damage paint if it comes in contact.After bleeding the M.C if you still can't build pressure,fill the M.C. open the bleeder & walk away for 20 mins or so & let gravity do the work.Than you should be able to get pressure.

[JohnC]

+1

Or, sometimes you can turn the handle bars so that the banjo bolt holding the line onto the master is down from the master itself, in which case you should be able to bleed it "normally".

[alantf]

Originally Posted by blaine

Have a rag wrapped around the fitting & line to capture any fluid coming out

I was taught to ¼ fill a jam jar with fresh brake fluid, then put the line under the liquid. That way, if it tries to suck air back, it'll suck fluid instead, so you're sure that it's all fluid in the system, after you've finished bleeding.

[JohnC]

Until the master is bled all you can do is pump a bubble of air half way out of and then back into the master. The air compresses and then expands again instead of pushing the fluid forward. Once the master is filled with fluid things can progress down to the brake caliper.

[blaine]

Originally Posted by alantf

I was taught to ¼ fill a jam jar with fresh brake fluid, then put the line under the liquid. That way, if it tries to suck air back, it'll suck fluid instead, so you're sure that it's all fluid in the system, after you've finished bleeding.

Yep.That's down at the bleeder.I was referring to bleeding the M.C. first.If you don't get the air out of the M.C. first,you will get nowhere.

[jonathan180iq]

All that being said, Namari, it's not impossible. Brake systems have to be filled from empty at some point in their lives. So you can do this.
Just, next time, don't completely empty the system