post-brake bleeding questions

[rideLIKEjehu]

did my first hydro brake bleed on the gs last night. it all went pretty well and it's always fun doing your own wrenching. came up with some questions after the fact as usual:

- i purchased one of those 'one-man brake bleeder' hose things (similar image here) and i couldn't get it to work for the life of me. the part that fits over the nipple had the metal teeth that got all bent out of shape and the other end is a spring-loaded mechanism with a hole in the middle that ended up dribbling brake fluid all over the place whether the pieces were tightened or not. i ended up just pulling all the fittings out and using it as tubing only, doing it the 'old-fashioned' way.

- i wasn't paying attention and i let the fluid completely drain out of the master cylinder so i'm pretty sure a bunch of air got in the system. so after i'd gotten all the old fluid out and most of the air, i disconnected the brake and bled it a few times above the master cylinder, so the bubbles would rise. i think i got all the air out, but how do i know?  all the manuals describe a 'spongy' feeling. i'm not quite sure what this means. is there any danger of air bubbles causing the brakes to fail?
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[The Buddha]

Yes air could cause brakes to fail. However your bike will let most of the air rise up to the Master cylinder in the first few mins of riding... cos of all the vibrations and jolts from the road. That leaves only the tiniest bubbles trapped in the most tightest of spaces. While that is still not advisable, and under heat it will expand and make the brakes not fully disengage etc etc... you'll notice the spongy feeling mostly as a weird squishy feel at the lever more than an actual problem. Of course ride harder and brake harder and all that changes. But otherwise weird feeling is mostly what you'll get. However bleed it and be done with it. The hose itself is not needed if you have Dot 5 in it. You can let Dot 5 get on plastic and paint, and it wont eat it. Once you ride a couple times around the block, I'd say press the lever, crack the caliper banjo bolt and tighten it back, then repeat with the master cyl banjo and the caliper bleed screw. all the while keeping the lever pressed. Then repeat. Should get rid of any air. Then top off the master cyl. The vacuum sucking thing they have is quite good BTW for bleeding brakes and even changing fluid.
Cool.
Srinath.

[rideLIKEjehu]

Once you ride a couple times around the block, I'd say press the lever, crack the caliper banjo bolt and tighten it back, then repeat with the master cyl banjo and the caliper bleed screw. all the while keeping the lever pressed. Then repeat. Should get rid of any air. Then top off the master cyl.

so i take this to mean i should bleed them again after a short ride to let all the air bubbles rise to the top? what do you mean by 'crack the caliper / master cylinder banjo'?

[octane]

In my experience, the one man kit only works with the vacuum pump. It has to fit AIR TIGHT or it's useless. The pump tube and caliper tube connect to a drain cup with a vacuum lid on it - each pulgging into the top. When you pump the hand pump, it builds pressure and draws fluid, air, and whatever else is in your brake lines into the cup. If you don't keep an eye on it though you'll bleed the cylinder dry and then you're starting over againn. Works well once you get the hang of it.

To answer your other question, it can't hurt to bleed them again if you're unsure. If they feel tight I wouldn't worry too much about it though. You'll recognize the spongy feeling if it's there. I generally bleed mine only from the caliper  fitting, not from the cylinder like Srinath described.

[The Buddha]

Once you ride a couple times around the block, I'd say press the lever, crack the caliper banjo bolt and tighten it back, then repeat with the master cyl banjo and the caliper bleed screw. all the while keeping the lever pressed. Then repeat. Should get rid of any air. Then top off the master cyl.

so i take this to mean i should bleed them again after a short ride to let all the air bubbles rise to the top? what do you mean by 'crack the caliper / master cylinder banjo'?

Well after a short ride... Bleed them like this. Put it on the center stand. Take the master cyl top off and press the lever. Hold it pressed, and open the bleed fitting on the caliper just ~1/4 or so turn (Just crack it open) ... just enough to get fluid out and as soon as fluid comes out shut it. Then let go of lever, and see if master cyl is still full. Then press the lever again hold it pressed and crack open the banjo bolt on the caliper. As soon as fluid comes out shut it, repeat with banjo at master cylinder.
The vacuum pump works more with speed than any technique. The fluid is sucked through the bleed screw quite rapidly, at some point in the process of sucking shut it so it cant suck any more. That point in time should be chosen based on, pure fluid comming out the bleed screw, and the master cyl remaining full from the start. Usually its a 2 man job. One man (or woman) to keep the reservoir filled and another to pump and close the bleed screw. Air tight connection is a must too but use a good new plastic hose and It usually works. It is a mess, and just for that reason I use Dot 5.
Cool.
Srinath.

[BadBatzMaru]

uhhh.... but if you are opening the bleed screw, and fluid is coming out... and you're free of air bubbles, then how can the reservoir stay at the same level??

I bled mine by hand, just by doing as you suggest.... just kept the reservoir topped off and repeated until the fluid coming from the bleeder screw was air free and fresh clean fluid (old fluid was definitely a different color...)  brakes feel fine, but havent tested them on the road yet (its 15 outside...) Is there something I might be missing??? like trapped air bubbles somewhere?

[JohNLA]

I bled mine by hand, just by doing as you suggest.... just kept the reservoir topped off and repeated until the fluid coming from the bleeder screw was air free and fresh clean fluid (old fluid was definitely a different color...)  brakes feel fine, but havent tested them on the road yet (its 15 outside...) Is there something I might be missing??? like trapped air bubbles somewhere?

That is all I did for mine and I have had no problems. I wouldn't worry about it  unless the brakes start feeling squishy.

[The Buddha]

well the reservoir wont be at the same level. It will drop but just a little. You dont actually move much fluid as in fluid flow when you hit the brakes. The fluid that is there gets pressurised and for 1 psi pressure at the lever the force (pressure times area) at the caliper is like 100 lb... am I close guys. It depends on the ratio of cross section area of the master cyl to the pistons in the caliper but I am sure its like atleast 40-50 times. So the brake line pressure will get fluid out, and not let air enter. But you dont let so much of the fluid out that the reservoir level drops significantly. between each bleed point you make sure the fuild is up to the mark. Also different color is due to water absorption. Dot 3 and 4 actually suck up water right out of the air. That's why you shouldn't use it from an open bottle. It also changes to brownish when it picks up water. Dot 5 is bluish to start with and doesn't take on water. Lovely. Use it from an open (non sealed) bottle 5 years later and its still fine. I have 5 year old Dot 5 to prove it too.
Cool.
Srinath.

[JohNLA]

Srinath, I looked for Dot 5 at the Auto Zone when I did mine but 4 was the best they had. Where did you find Dot 5 ?

[The Buddha]

I have bought it at pep boys, napa and advance auto, and even Kragen. I haven't looked at autozone specifically though. Bike stores do have them, and dont buy 5.1. That is synthetic 4, not silicone based like 5.
Cool.
Srinath.