Bleeding the brakes - the impossible task?

[Adamastor]

Hi everyone...

here I am once again, another day, another doubt and another problem...

As some might know, I have been doing a lot of tasks to get my new R65 back to the road.. The last task involved buying a new cylinder/piston and that resolved my previous problem with low compression.
But when you think now all will be ok, there's always another problem ..

I had a warped front disc (dual disc brembo caliper) so I bought a used one, but in good condition. I believe that disc warped because the caliper was not fully retracting. I cleaned both calipers, seals seemed really ok and they weren't really dirty.
I decided to also buy new brake hoses, which I did and installed them.
Now to the big task: Getting air out of the system... after surfing the web I decided to use the syringe method filling the system from bottom to top. It all went ok.
I get pressure at handle but even after hundreds of times pushing the lever I still see bubbles of air getting into the brake oil container.
I left the handle under pressure over night, I gave little taps all over the hoses, etc etc but still keep on getting too much air. There shouldn't be any air bubbles on a normal system, right?
Both calipers also seem to drag a bit, could it be that bubbles dont let the oil rise well?
I see no apparent leaks and even with pressure overnight, the handle didnt move farther (would be a leak sign, right?).

I am not familiar with bleeding the brake system on these bikes, and never have done similar with another bike (never replaced hoses before, just did the normal change of fluids not letting air getting in), so I need you to give me your advice?

- Should I keep on pressing the lever and trying to see if all the bubbles get out?

-Should I keep more nights the lever with pressure? How much pressure is enough?

-What else could be wrong? A damaged brake cylinder would make this kind of problem?

Thanks in advance for all your answers... I wanna ride my bike!

[Bob_Roller]

You may be getting air from around the threads of the bleeder screw, not from the brake hydraulic system .

If you have some teflon tape, wrap a thickness or two around the threads only to prevent air from getting in .

[nhmaf]

I just bleed my brakes with what is called a "third hand" in auto stores in my area - it is just a check valve that helps one to bleed the air out through the "normal" bleed screw - where you attached your syringe.   I would think that your method should result in very little air remaining in the system.  Did you still have the top cover on (but screws loosened) the m/c reservoir when you did it?   Though it makes for a bit more potential for spillage, I usually leave the cover and rubber bellows off when I am doing mine - I do tend to use lots of rags to catch anything from falling on a painted surface.  

One the air is bled out, no more air bubbles should come into the system, unless there is a leak somewhere.  

[Bob_Roller]

I've used a vacuum bleeder for about 25 years, and never had a problem, but you draw in air around the bleeder screw, that's what the teflon tape is for .

[montmil]

Some years back, I built a hot rod FAA licensed Experimental Category aircraft. The brake pedals were part of the rudder control linkages; buried way under the instrument panel. Basically all but impossible to attach hydraulic fluid fill equipment.

Solution was to fill the system from the Cleveland disc brake's bleeder screw upwards through the tubing and into the fluid reservoir. The technique pushed air ahead of the fluid. No bubbles.

If you've replaced brake lines and have clean caliper components, this may work for you. Keep a weather eye on the handlebar reservoir. No need to slop the juice onto the paint!

Auto supply stores carry a vacuum tool called MityVac. It's an economical tool for your needs. Check one out.

Monte  

[larstorders]

The air bubbles want to rise upwards.
BUT, the bleed nipples on your calipers are way down below the brake lines and the brake cylinder.
The cylinder can't push enough fluid in one stroke to move all the fuid in the brake lines and trapped bubbnles out through the nipple in one stroke. Therefore as soon as you allow the lever to return to take a second stroke the bubbles float upwards back up the brake line.
So, to help the air bubbles find their way up the brake lines and back out through the brake cylinder I agitate the brake hoses by tapping and wiggling them quite vigerously. This helps the bubbles negotiate any bends and joints in the system. At the same time I pump the lever steadily and all those bubbles come out into the reservoir. I don't open the bleed nipple during this procedure. I wait till no more bubbles can be seen then bleed through to finish off the job and to get fresh fluid into the lines. Hope this helps.

[MrRiden]

You mention that the brakes drag. I just recently ran into this on a '83 R65. There is a pressure return hole in the master cylinder, visible when looking down into the master cylinder reservoir. It is the teeny tiney hole of two down in there. If this becomes blocked pressure on the calipers will not fully release and you will have dragging of the pads.
  As far as the bubbles go I agree with lastorders. Try a rubber band or two on the brake lever to hold it back overnight. You don't need pressure on the handle per Se, just enough to hold the lever back so the passage way in the master cylinder is open. Getting all the air out of a newly rebuilt system can be vexing. The only other wisdom I can offer is a line I found in a manual for a different make of bike. Per Haynes book for Triumph twins, in the gearbox section it  states "May take several attempts" Good mantra that!

[Adamastor]

Guys, you totally rock!

Thank you all for the tips, I added some teflon tape to the bleeder screw and have done once again a bottom to top filling of brake oil.
Guess what? No more bubbles!!!! This is wonderfull.. I got brakes once again, and no more drag...

Thanks thanks, many thanks... I had spend so many hours trying to figure that out

Now... to the next problem...  

[Justin B.]

One more tip, if your lever still feels a bit soft then squeeze down on it and secure with a tie-wrap overnight - it'll be rock hard the next morning unless you have a problem of some kind...

[joshr65]

I use these...

http://www.speedbleeder.com/

Work perfectly!