More front brake bleeding problems

[AKMac]

Ok, today I got the new master cylinder, and SS brake lines. I still can't get these brakes to bleed. So far I've replaced the master cylinder, lines, rebuilt the calipers, and replaced the bleeders.

I've taken the calipers off, hung them above the junction block, used a vacuum pump, and still nothing. I've even tried bleeding the old fashioned and in every possible combination/angle I can think of.

I can see a little fountain in the master cylinder so I know it's pumping. I can also see the caliper pistons moving just a little, but it's not enough to get any braking action.

What next?

[DiverRay]

AKMac,
Did you "bench bleed" the master cyl?
With the banjo bolt off the master cylinder, put your finger over the hole, squeeze the lever, cover the hole, and then let go of lever. Repeat until fluid starts to squirt out when you squeeze the lever. Reconnect everything, and proceed with the bleeding.
Ray

[dragxs11]

A little trick I learned is to compress the cyl. slow, and then let it snap out. The air wants to come up, so this action helps it get to the top. Of couse, it only works if everything else is in proper order.
And howdy to DiverRay. How've you been? Dunno if we're having a rally here this year. I'm all growed up and busy with a wife and house now.

[AKMac]

Well I took the brake hose off, and when I pulled the brake lever the fluid would almost blow my finder off the opening.

DragXS - I've been trying your method too without any luck.

I also got a little oil gun and tried to reverse bleed the brakes without any success. In desperation I just took the bike for a little 10 mile ride with only rear brakes and I still have nothing.

When I rebuilt the calipers could that have done anything to cause this problem? Also, how for down do your bleeders go into the caliper? I can still see a little bit of threads on my bleeders.

Well I'm going to let it sit overnight with the brake lever tied down in hopes that some air comes out. I'm truly stumped.

[dragxs11]

Ok Mac, I think I've been here before and I think we can figure this out. This little fountain that you see should not happen when you squeeze the brake. It's been awhile since I worked on brakes. I don't think you should get a fountain unless you've got pressure on the discs. If it does, it means that the master cyl diaphram can't be working properly. When you squeeze the brake the diaphram is supposed to pull fluid from the reservor and the pressure from the pads on the discs causes the fluid to come back into the reservor. It sounds like your not passing fluid through the holes in the diaphram. When you say the cyl. is new, is that NEW or new to you? If it's rebuilt, I know the rubber seal in there can get shoved to the other end of the diaphram shaft. That would do it. Wish I had a pic so you could see how it works. Judging from your bike, your obviously not an idiot. You probably know exactly what I'm talking about.
Matt

[AKMac]

The master cylinder is a brand new partsnmore replacement. I've been very careful to not to depress the lever to far as to unseat the rubber seal. However, I may have done it inadvertently. I just checked my master cylinder and it does have a fountain when I pull the lever.

I have to work tomorrow, but Thursday I might try rebuilding the old master cylinder to see if I can get that thing to work properly. At least that way I'll know what the problem is.

[dragxs11]

MMM , The partsnmore cyl. worked pretty good for me. That surprises me a little. I'm sure it works the same way, but I've never had to take it apart. I think what Ray was talking about with the bench bleed is to put you finger over the banjo bolt hole after the lever is pulled in, then let the lever out. This should force the diaphram to pull fluid from the reservor. If it blew fluid around your finger, that washer is most likely still in place. I find it a little hard to believe that master cyl. is bad. It seems to me to be a much better(and prettier) design than the original. Mine was pretty much plug and play.

[TopCatGr58]

Hey AkMac,

I had one of my calipers that wouldn't bleed properly, turned out the old bleeder screw was CLOGGED, and even though I was turning it loose, a little fluid would leak out around the threads of the bleeder, but not THRU it, and so could not evacuate the air and fluid properly!!!

Pull your bleeder out and check to make sure the ports are open and that fluid/air can pass thru it! Also, do you have a clear tube to put on the end of the bleeder screw, so that you can see the fluid and air bubbles escaping!?
T.C.

[AKMac]

Well my bleeders are new. I figured they're cheap enough to replace so I just bought new ones.

Ok, does this makes sense to you guys? I was talking to on of the airplane mechanics at work about my problem and he suggested that I try pumping the handle very fast. Eventually this will cause the air to compress enough that I should feel a little bit of pressure on the lever. If not, something isn't working with the master cylinder.

I just tried this and no matter how fast I pumped the lever I couldn't get any pressure to build up. Maybe my new master cylinder is defective.

[TopCatGr58]

Hey AkMac,

I had to pump mine fairly fast after putting on the new brake lines, hard to tell if anything was going thru the lines, but just kept pumping 3 times, held, released bleed screw, then retightened, and repumped, repeated many times, but finally saw the fluid and bubbles flowing out of the clear tube attached to the end of the bleeder valve! Worth a try!
T.C.