Problem bleeding the front brake after complete overhaul

[Gongal66]

Hello everyone, first time posting here!

Sorry for any grammar errors, not my main language.

So im doing a complete overhaul of a 1993 GS500E, and i have it almost finished, but i found one problem: cant bleed the front brake.

I rebuilded the master cylinder and the caliper with new seals, everything went well as it was pretty easy.

The problem comes when i try to bleed the line, it just doesnt build up any pressure.

At first seemed like i was getting some pressure, the brake was able to stop the wheel from spinning, but the handle was loose, so i tried bleeding it a bit more and loose now doest have any pressure at all.

The bike has already an aluminium brake line, it was upgraded by the previous owner.
The master cylinder seems to work fine, because doing the trick of blocking the banjo bolt hole with my finger i can feel a the pressure.

It is not leaking anywhere.
Im using DOT4 brake fluid. Im already bleed the rear brakes and it was a pretty easy job, so im a bit lost with this now.

Any idea what can cause this? Maybe a bad brake line? I was thinking in replacing it in a future anyway

[mr72]

do you have fluid leaking somewhere? that would indicate a bad brake line.

Motorcycle brakes are notoriously difficult to bleed. I bought a brake bleeder kit to do mine, FYI.

However, if you overhauled the caliper and you have no brake pressure, I would suspect some error in the caliper overhaul. I'd try a brake bleeder first, then go back and tear the caliper down again.

[Gongal66]

No, it doesn't leak anywhere. Gonna check if everything in the caliper is seated correctly.

[chris900f]

I think you have air in the line. This is what I do:

Open bleeder--press lever--close bleeder--release lever.  Repeat until no more air bubbles appear in the drain hose,

You will have to refill the open reservoir a few times to purge the line; it helps to have an assistant work the bleeder valve.

Also, I recommend a small box-end wrench be used on the valve, because you will need to open and close it several times.

After a few cycles the you should feel the lever resistance begin to increase when pressed with the bleeder valve closed.

[Gongal66]

I think you have air in the line. This is what I do:

Open bleeder--press lever--close bleeder--release lever.  Repeat until no more air bubbles appear in the drain hose,

You will have to refill the open reservoir a few times to purge the line; it helps to have an assistant work the bleeder valve.

Also, I recommend a small box-end wrench be used on the valve, because you will need to open and close it several times.

After a few cycles the you should feel the lever resistance begin to increase when pressed with the bleeder valve closed.

THIS WAS THE SOLUTION! Thank you very much, i was able to get it working this way.

[Bluesmudge]

I think you have air in the line. This is what I do:

Open bleeder--press lever--close bleeder--release lever.  Repeat until no more air bubbles appear in the drain hose,

Isn't the correct method actually:

Press lever -- open bleeder -- close bleeder -- release lever. You pre-pump the lever before cracking open the bleeder to make sure no air gets into the line from the bleeder end.

[chris900f]

I think you have air in the line. This is what I do:

Open bleeder--press lever--close bleeder--release lever.  Repeat until no more air bubbles appear in the drain hose,

You will have to refill the open reservoir a few times to purge the line; it helps to have an assistant work the bleeder valve.

Also, I recommend a small box-end wrench be used on the valve, because you will need to open and close it several times.

After a few cycles the you should feel the lever resistance begin to increase when pressed with the bleeder valve closed.

THIS WAS THE SOLUTION! Thank you very much, i was able to get it working this way.

That's great!!

I went through a litre of brake fluid before I figured it out, back in the day.

[chris900f]

I think you have air in the line. This is what I do:

Open bleeder--press lever--close bleeder--release lever.  Repeat until no more air bubbles appear in the drain hose,

Isn't the correct method actually:

Press lever -- open bleeder -- close bleeder -- release lever. You pre-pump the lever before cracking open the bleeder to make sure no air gets into the line from the bleeder end.

Yes, you are correct there Smudge...it was pretty fricken late to be awake and posting after the day I'd had. but it all worked out regardless.