Rubbermount_EVO DOT 5 Flush/Bleed Routinely?

[John Harper]

Originally Posted by Bacnine53

Tied brake grip to handle overnight to get bubbles to rise to master. Still no firm brake. Have a reverse bleeder coming to try.
Any suggestions will be appreciated.
Bob

Aren't you closing off the system by tying the lever to the grip? As the M/C piston pushes, doesn't it close off the reservoir, so it can push the fluid in a sealed environment? I've heard of this method but it never really made sense to me. Maybe I'm wrong, or maybe it doesn't really matter?

I just opened the bleed screw with a short piece of aquarium tubing attached and pointed up. Filled the M/C reservoir, and just waited to see fluid in the tubing. I just left the lever alone, away from the grip. After that, a couple bleeds and lever was solid. I think it took about a half hour, enough time for a beer.

John

[Hippysmack]

Yes, pressurizing the system and letting air flow up to the piston.
Removing the ties on the lever later is suppose to suck air that may have settled up top to re-enter the reservoir.
With the pressure from below assist when the lever comes back to normal position.

[John Harper]

Originally Posted by Hippysmack

Yes, pressurizing the system and letting air flow up to the piston.
Removing the ties on the lever later is suppose to suck air that may have settled up top to re-enter the reservoir.
With the pressure from below assist when the lever comes back to normal position.

That does make sense, thanks. I found letting gravity do it's thing was quite easy, at least for the front brake.

John

[roachhill]

Dots has a much longer life span than other brake fluids. It was developed for the military so vehicles could be stored long term.
Since even small drops mixed between dot 5 and other types of brake fluid can cause catastrophic brake failure once a system has dot 5 in it you can never go to a different fluid.
Does this mean you would need a separate bleeder for dot 5 to avoid cross contamination?

[hbsporty]

I have tied the levers before. I don't pull them verry tight, just enough to open system. Works fine.

[cookiemech]

No trouble whatever flushing and bleeding the front brakes with fresh DOT 5 fluid, using my vacuum bleeder.

When I tried the same with the rear, no fluid came out with the vacuum bleeder. I could not even pump fluid through, and the pedal had very little resistance. I removed the rear master cylinder and rebuilt it with a kit purchased on line. Nothing was obviously wrong inside it; no pits in the cylinder, no torn cups. I dunno, maybe the cups hardened or something.

Anyway, reassembled, filled reservoir, vacuum bled, and all is well.

[Deimus]

Sounds to me like a lot of "over thinking" is going on here regarding the DOT5 bleeding. I bought my 2005 XL1200C new and still have it. I installed braided SS lines long long ago, I also changed the front caliper (also long ago), and I had to replace the rear master cylinder years ago due to the original one failing; anyway, all that to say I've worked on the brakes many times. I always use a vacuum brake bleeder (a Mityvac hand pump version) to initially bleed the brakes. Then each morning for the next several days, depending on the feel, I pump up the brake and quickly crack the bleeder and close it. That's all it takes to restore a rock solid brake action. The DOT5 fluid holds micro-bubbles that need to migrate to the bleeder each night for a few days. Once those micro-bubbles are gone your feel will be solid. Don't over think the process.

Regarding cross contamination, if you use a vacuum bleeder no fluid ever goes backwards into the system. Actually, if you are working the bleeder valve properly, no fluid will ever go backwards anyway.