E.Marquez

The idea is air in the calipers and lines will rise overnight, and pass though the return port into the reservoir, some swear it works, many others swear at it for not working, your mileage may very.
I have tried the method out of curiosity, I don't feel it worked to remove all the air from the system.. and in general, I don't have time to wait over night for a partial job i'll still have to finish bleeding in the morning.

There is merit to getting air out of the system through the return port...its part of my three step brake bleeding process.
Power bleed till system is full and showing no signs of air coming out.
Move the bike and Master though various angles and orientations while squeezing the lever in slowly and letting it "snap back" the vibrations will help move bubbles and you'll see a bit of air come up though the return port, once no more air.
Power bleed again...and done.

IF there is still air trapped which can happen, back bleed.

On really stubborn systems, if the brakes are working well enough to safely ride... Go ride....let the vibrations work for you, and the movement of the bike left, right, front real, ect as well.
NOTE: That above is for non ABS bikes...

ABS bikes it s power bleed only with activation of the ABS unit to open up passages, ports, valves ect.

Wolverine

I've been discussing this on the Ducati forum. I don't buy in. I need logic and scientific reason and what I see lacks it. But those guys are mainly talking about the rear brake circuit, where the ABS pump under the seat is the high point.


So I say hog wash! Just because some old timer did it and you feel a placebo effect doesn't mean it works.

When you depress the master cylinder piston, the first seal moves past the openings to the res, sealing the system to build pressure. That air is going to travel to the absolute high point in the system, which is not always the master cylinder.

I am open minded. Show me the evidence and I will easily buy in.

E.Marquez

You have a bike or two in your garage?
The evidence to support or denounce the procedure is in your hands

Wolverine

All my junk has air-free hydro systems...

smokinjoe73

I got a bleed nipple / banjo bolt for the master. This way I can just bleed it there. It is very effective since of course air bubbles rise to the top of the system. Saves me a ton of time.

bigborer

The way I see this working is: tie the lever closed > get pressure inside the system > pressure compresses air > air tries to escape > air goes up. The default position of the MC is open, so after you release the lever the air "should" just exit through the MC.

I've had mixed results with this- in some cases the air still remains trapped somewhere, probably right before the MC or in the lines. At best it got the brakes from **** to usable, or from usable to good, but never from **** to great. At worst it just didn't do anything.