HELP! No pressure on brake lever after removing banjo bolt

[dartagnanphd]

I've been a longtime lurker in this forum and am finally making my first post!

Bike: 1982 GS650G

This has been a project I've been working on for 7 months... last owner wrecked this thing. Finally have it running, so I thought I'd flush the master cylinder because it was looking a little murky. The front brakes were working, but I wanted to make sure everything was tip top.
I loosened the banjo bolt on the right side caliper to access the bleeder screw, because the brake line was very very close. Then, caput! No pressure at all in the brake lever. I bled the brakes on both sides, went through a whole bottle of brake fluid, nothing, no resistance at all.

Things I've tried, per this forum's advice:
-I removed the brake line from the MC, but my finger on the outlet and pumped the lever. Felt pressure, but lever is still soft as can be
-I removed banjo bolts from both calipers, held my fingers over the outlet, pumped and felt pressure. Nothing.
-I investigated the "little hole" in the MC, it is doing fine and I see activity when I pump the handle.
-I took apart the calipers, cleaning the boots, inspected the piston, nothing.
-I pumped the brake with the calipers off to see if the piston was moving, it wasn't.

I'm totally at a loss... I am unsure why this happened. My gut tells me there's air in the line but I'm not sure how to get it out if there is...

I thought that maybe the caliper pistons became seized but I cannot see how that would be.... they were working fine before.

Any help would be much appreciated!

[salty_monk]

You need to "prime" it. You can either crack the banjo bolt while pulling the lever or the easier way is to either apply suction from the caliper end (via the bleeder screw) or inject brake fluid from the bottom using a syringe.

Personally I use the suction type bleeder tool. Harbor Freight has a cheap one that's not awful.....

[dartagnanphd]

Noted! I have already tried sucking from the bottom using a syringe... the fluid came out clean with no bubbles but still no pressure on the lever! I will try the cracking the banjo bolt though.

[bwringer]

I'm guessing that you accidentally slurped some air into the master.

To get the last of this, you have to remove the lever, loosen a bleeder somewhere or the MC banjo (with a rag around it), and push the piston alllllll the way in with something suitably pokey and blunt that won't scratch the bore if it slips. A dowel or similar works well.

[dartagnanphd]

Great advice! I will give that a try to-day. Do you guys think that a vacuum bleeder is necessary in this case? Something like a mityvac? I’m trying to avoid buying one but other posts say it works like a charm.

[Nessism]

If you haven't replace the brake lines already, I'd put your project on full stop and do that now. Your old rubber lines are sure to be dry rotted, and full of crud inside.

You say that you cleaned the pistons, but did you remove them from the calipers in order to do so? If not, that's also needed. Same for the master cylinder. Remove the piston, clean, and inspect.

[dartagnanphd]

Im not sure if my front lines are rubber… they look to be metal of some kind… will upload pictures.

[salty_monk]

Brake bleeding tools are super cheap now... Amazon has them for 15 bucks if you don't like harbor Freights $25 version. Bwringer's tip is a good one. I've never needed to do that with a vacuum bleeder though.

With the syringe you want to push clean fluid UP into the lines (to push the bubbles out the top) not used it to suck fluid through, that won't work.

No one has checked but I assume you know the correct procedure for bleeding? Little bit of pressure on the lever, crack the bleeder, shoot the fluid through by pulling lever all the way, close the bleeder - only at this point can you release pressure on the lever... don't let the MC run dry at any point.

[dartagnanphd]

Mr. Monk, great advice! Was hoping to avoid buying another tool…
yes, I read extensively all the proper bleeding tips on other forum posts, especially the ones from Mr. Cliff. I think y’all are right and there’s some stubborn air in the MC. I will attend to this to-day and report back!

your advice is all very appreciated

[dartagnanphd]

UPDATE:
I removed the handle and pumped the MC piston with a pencil while the banjo was removed. Nothing.
I forced fluid in through the bleeder screw using a syringe, nothing.
Air coming through the bleeder line was bubble free and clear.
I'm beginning to wonder... is it possible a my caliper pistons are seized? They are not moving at all!

[salty_monk]

It's possible but even with seized pistons you should still be able to bleed it.....

[dartagnanphd]

Hmmm… I mean it does bleed, fluid is coming out of the bleeder screws and very little air is coming out, but no pressure. Why would the caliper pistons not
be moving as I bleed?

maybe I’m not bleeding long enough… I put around 8oz of fluid through it already and no pressure whatsoever

[salty_monk]

There is no pressure on the piston when you are bleeding. They won't move.

You have an air bubble in there. The fluid is passing over it but when you pull the lever it compresses it....

Are your bleeder screws the original ones? I've heard of people having issues getting a seal on "new" bleeder screws. Perhaps for a test try putting some teflon tape (pipe tape) on the bleeder screw threads & try again....

[Rijko]

I investigated the "little hole" in the MC, it is doing fine and I see activity when I pump the handle.

Just to make sure, there are 2 holes, one small and one tiny bleeder hole ?

if the brake pads are near the discs, there is a large space behind the caliper pistons where air could be trapped.
If you push the pistons into the calipers as far as they will go, that space is small.
Saves time bleeding, and less air trapped there preventing pressure.

Tie something like a rope, or tie-wrap, around the throttle grip and brake lever with the reservoir cap off
and leave it overnight, may help.

Air wants to travel up, but gets trapped easily.
Sometimes turning the handlebars allows air to rise.
With the bleed nipples closed, reservoir cap off, repeatedly slowly pump the lever and see
in which handlebar position most bubbles rise.
Tapping the handlebars while doing so sometimes helps.

[dartagnanphd]

After some digging, I tested the master cylinder outlet by putting my finger over the outlet with the banjo removed. There was some pressure, but it was negligible. An acquaintance informed me that the pressure from the mc should be substantial, so I think I might have some issues with the seals. I am on the verge of buying a master cylinder rebuild kit, what do yall think Rijko salty_monk Nessism