Rear brakes not engaging after rebuild

[cruzanron]

Here is my latest problem that I hope someone can help me with. When I got my project 83' GL1100, the rear brake pedal was seized (typical problem) I fixed that issue and rebuilt the rear master.cylinder and the caliper. I bought a fancy vacuum bleeder and reverse bled the lines from the caliper (filling the reservoir). I cannot get the pistons to engage and grip! I'm so frustrated, re-re-built the caliper and master cylinder and bled the system no less than 10 times. I do not see any fluid leaks in the rear brake lines. Any ideas here? Thank you very much for suggestions. I don't see anything helpful on YouTube or goldwingdocs.

[WingAdmin]

Can you get any pressure at all on the brake? Or is the pedal just flopping down like there's no fluid in there?

If you have any pressure at all, try tying down the pedal (I use a bungee cord) - pump it several times, push it down hard, and fix it in that position. Then let it sit like that overnight. This will often allow small air bubbles to migrate through the system and out of the lines. I've had to do it two or three times on a rear brake before getting a solid pedal, the front usually works with one go.

[DaveO430]

I see you have an 83, did you also bleed the right front (or is it left, can't remember), it is linked to the rear brake.

[cruzanron]

It has no pressure or resistance in the pedal at all, but limited hydraulic pressure is going to the caliper bc when I open the nipple while holding down the pedal, some fluid comes out but not at good pressure like your expect. Well, after realizing that it's an '83 with linked rear brake with the front right caliper, I was excited to get home at lunch break today to blead the front praying that it will be the magic cure. It was not. The was a little air in the front line. I purged that the same way I did the rear. I cleaned the nipple and banjo bolt, attached the bleeder to the front right nipple and pumped fresh fluid backnthrough the system until the reservoir was full. A couple of big bubbles surfaced that's it. The pedal is still not gaining tension or stiffness. I'm at a loss. I'm starting to think that somehow my Master Cylinder is bad, but with a new gasket kit, it's hard to see how that's possible absent a structural crack or something, which I have not seen. Any more ideas? Maybe the rear/front proportioning valve?

[WingAdmin]

It has no pressure or resistance in the pedal at all, but limited hydraulic pressure is going to the caliper bc when I open the nipple while holding down the pedal, some fluid comes out but not at good pressure like your expect. Well, after realizing that it's an '83 with linked rear brake with the front right caliper, I was excited to get home at lunch break today to blead the front praying that it will be the magic cure. It was not. The was a little air in the front line. I purged that the same way I did the rear. I cleaned the nipple and banjo bolt, attached the bleeder to the front right nipple and pumped fresh fluid backnthrough the system until the reservoir was full. A couple of big bubbles surfaced that's it. The pedal is still not gaining tension or stiffness. I'm at a loss. I'm starting to think that somehow my Master Cylinder is bad, but with a new gasket kit, it's hard to see how that's possible absent a structural crack or something, which I have not seen. Any more ideas? Maybe the rear/front proportioning valve?

I've never reverse bled a linked braking system, I don't know if you end up pushing the same air bubbles back and forth. In fact, I've never reverse bled anything except an airplane.

If your pump will do vacuum bleeding, you might want to try that - I've never had that fail on a Goldwing. Make sure you do the front caliper first, then the rear.

[dingdong]

Just thinking here... Are you sure you have the new seals in the master cylinder installed facing the right direction? I have seen it happen.

[cruzanron]

I'm pretty sure. I even re-did it and contacted the manufacturer to ensure I had the right kit. I'll take apart again and take pics

[OldguyGlen]

Doing similar total rebuild of brakes, MC's and Calipers. Still in pieces at this point, but I've done some trial bleeding, and repeatedly re-bled while doing pressure style forcing of pistons out of the seized assemblies. It takes only a minuscule amount of air to diminish actuator pressure. The rear is also handicapped since the hose is NOT all uphill to the MC, like the front. And the splitter to the front adds more possible air traps. Vacuum bleeding is best. Air gets trapped down around the piston itself after rebuild. I don't have a vacuum tool, So I pumped the lever, strapped it down, repeatedly tapped the caliper with a hammer handle to "jiggle" the bubbles up toward the bleeder, opened the bleeder and got a few bubbles... then repeat process multiple times.
You can also take the caliper off its mount (hose attached), and carefully (with a temp stop in the jaws to prevent piston separation) allow piston to extend while pumping, and then press it back home as part of the "expel" the bubbles part of the bleeding cycle. You move more fluid volume flow that way to get air out of tiny spaces around the piston.

[cruzanron]

PROBLEM SOLVED!!!! Thanks to all of the helpful fellas on this page. I took a suggestion from another member and tied the rear brake pedal down for 30 hours. I just checked it and I have great pressure and resistance against the pedal. I gave it another traditional bleed without the tool and it had zero air. I am so relived and grateful to all of the helpful guys on these pages to help keep these classy ladies on the road and out of the junkyards....because I was close. Lol

[WingAdmin]

PROBLEM SOLVED!!!! Thanks to all of the helpful fellas on this page. I took a suggestion from another member and tied the rear brake pedal down for 30 hours. I just checked it and I have great pressure and resistance against the pedal. I gave it another traditional bleed without the tool and it had zero air. I am so relived and grateful to all of the helpful guys on these pages to help keep these classy ladies on the road and out of the junkyards....because I was close. Lol

Glad to hear it. That works pretty much all of the time on these bike brakes if there are no other problems.

[cruzanron]

Thanks. I'm so relieved that this took care of the problem without buying more parts, esp that proportional valve that's no longer available. I've already blown my restoration budget so this fix was a welcomed surprise