Rear Caliper Upgrade Problems: Advice/Help Requested

[aplunkett6789]

Howdy, folks!

@bowtie39 sold me a front caliper that @jim snyder modified to fit the rear. Threw some new EBC sintered pads in there while I was at it. Put it on, buttoned everything up, but I can't for the life of me get a pedal out of it. I have a Phoenix Systems V-5 bleeder - I've used it on multiple cars with great success - and I've tried sucking fluid out, reverse bleeding, but I don't know....

When I have the bleeder cracked and press the brake pedal, it spurts fluid out, but not too powerfully. There's no leaks that I see.... this is frustrating.

With this new caliper mod, do I need a longer brake hose? It reaches, but I'm a little weirded out by the position.... tell me if I'm just being a ninny (see pics).

Another thing I noticed is that with this setup, the bleeder is no longer the highest point on the caliper - the banjo bolt is. Could this be why I'm not able to properly bleed it? I figured that the pressure bleeder would pull all air out of there, and leave only fluid, but no matter how many times I pump I'm still getting some aeration....

How do I check to see if the master is bad?

Getting tired of little things turning into big projects... JUST WANNA RIDE!

Thanks in advance.

 

[jim snyder]

I've bled several of these units and never had an issue. I just had the same issue with my FJR and had to replace the rear master cylinder. Also check the caliper pucks and be sure they are moving freely.

 

[aplunkett6789]

I've bled several of these units and never had an issue. I just had the same issue with my FJR and had to replace the rear master cylinder. Also check the caliper pucks and be sure they are moving freely.

Thanks, Jim - that's tomorrow's job. Thanks for doing such a great job with this caliper mod, BTW.

 

[aplunkett6789]

Does anyone know of a way to test the master cylinder to determine whether it's not good, or is it just by process of elimination?

 

[Jpd11958]

The normal test for a master cylinder is to push and hold. If it creeps down, it is bad. I had a front that held if I applied fast but didn't if I applied slowly. It would keep moving until it bottomed out. 1 slow push and you should be able to fully apply the brakes to a firm peddle. You should also be able to see the wheel cylinder flex as it squeezes the disc.

 

[aplunkett6789]

The normal test for a master cylinder is to push and hold. If it creeps down, it is bad. I had a front that held if I applied fast but didn't if I applied slowly. It would keep moving until it bottomed out. 1 slow push and you should be able to fully apply the brakes to a firm peddle. You should also be able to see the wheel cylinder flex as it squeezes the disc.

Great, thank you. When I press on the brake on mine, the pedal goes all the way down and it does not hold. So, either there is air in the lines, the caliper is bad, or something is happening so that the master cylinder does not build up any pressure. Tonight I will test my caliper to make sure the pistons move, and then I will try one last time to bleed any air out of the lines. Then I will report back.

 

[Mercer]

For what it is worth.
I had a hell of time once with my front on C10. Could not figure why!
Bled every which way. Pulled it all apart could find no issue.

Took it all loose from bike and hung it so all was in a straight line as best could
with a band holding master in semi compressed state. Used some plates to keep calipers from collapse.
Trapped air had no place to go but up. Left it overnight as so.

Got trick off net somewhere.

Next evening got enough "pedal" to get it all bled and working satisfactorily.
Still to this day have no idea why it was such a PIA. Would say if a pump it "lost it's prime".

Was it worth the trouble?
Can not say, but I was waiting rebuild kits so had time to spare.
Still have kits. Have not used them yet.

Oh, got into situation in doing seasonal fluid exchange for soft feel. Sucked air by not keeping
master full if I remember correctly. Senior moment maybe. Not paying attention maybe.

Have my wife keep it full now as a precaution.

 

[aplunkett6789]

For what it is worth.
I had a hell of time once with my front on C10. Could not figure why!
Bled every which way. Pulled it all apart could find no issue.

Took it all loose from bike and hung it so all was in a straight line as best could
with a band holding master in semi compressed state. Used some plates to keep calipers from collapse.
Trapped air had no place to go but up. Left it overnight as so.

Got trick off net somewhere.

Next evening got enough "pedal" to get it all bled and working satisfactorily.
Still to this day have no idea why it was such a PIA. Would say if a pump it "lost it's prime".

Was it worth the trouble?
Can not say, but I was waiting rebuild kits so had time to spare.
Still have kits. Have not used them yet.

Oh, got into situation in doing seasonal fluid exchange for soft feel. Sucked air by not keeping
master full if I remember correctly. Senior moment maybe. Not paying attention maybe.

Have my wife keep it full now as a precaution.

Thank you! I was hoping to do a little more diag today, but didn't get around to it. Sometime this week I'll check caliper pistons for movement. If all's well there, I'll give what you mentioned a shot and see if it helps before I go the rebuild route for the master. If I'm understanding correctly, I would remove master/caliper assy, and hang it with caliper at the top, and the master semi-compressed? Do I leave bleeder open, or closed, and allow air to get trapped at top?

 

[Mercer]

Thank you! I was hoping to do a little more diag today, but didn't get around to it. Sometime this week I'll check caliper pistons for movement. If all's well there, I'll give what you mentioned a shot and see if it helps before I go the rebuild route for the master. If I'm understanding correctly, I would remove master/caliper assy, and hang it with caliper at the top, and the master semi-compressed? Do I leave bleeder open, or closed, and allow air to get trapped at top?

From memory I used coat hangers to get master and calipers in a vertical line. Still attached at "t". This with lines straight as practical the calipers were almost upside down. Bleeders closed. The master and lever was positioned to just hold a little fluid over open ports in bottom.

Was thinking air was trapped somehow in calipers and not bleeding fully.

In your circumstance in rear you will have to deviate and adapt procedure would think.

Note also I have started using grease around bleeders when bleeding. Seems to eliminate pulling air around bleeder threads and giving false air bubble indicator. Neat trick.

Hope this helps. Only ever had to do this once. Has not happened on subsequent bleeds.