need help diagnosing brake issue

[Eman]

Originally Posted by GallopinGhost

Eman, yes you are correct on what I have done. Checking with the lines plugged sounds like a good step. If it's determined I need more volume in the MC, how is that spec listed ? I have an adjustable push rod on the MC, maybe if I can get a longer throw that might help. Check valves also seem like it's worth a try.



The thing that bugs me is after a few pumps of the pedal, all is good.





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I'd say the reason the pedal gets better when you pump it is the pads move out towards the rotor with the first pump so they have less to travel on the next pump. People tried springs to push the pads back and eliminate any drag from the pads rubbing the calipers. What happened was the first pump went almost to the floor. Just like when you do a disc brake job and push the piston back. You have to pump the pedal to move the pistons back out.
Someone mentioned pedal ratio which is important, usually 6:1 or better. You also have to be sure that the pedal can push the MC all of the way to bottom. You them have to be careful when you adjust the pushrod as sometimes you can cause brake drag especially when the brakes get hot.

[GallopinGhost]

Pedal ratio is 7:1


Ok, I have a game plan.



1) going to check out MC pushrod travel and see if I'm getting a complete stroke.


2) Since I've been swapping lines on the MC, I will thoroughly bleed the brakes again, then as mentioned, remove the lines at the caliper and cap them. Not sure what I will cap them with, but a short flare plug would be great as not to add a lot of air.


3) If the light bulb doesn't turn on at that point, I'll add a couple of check valves to the MC. I see they're only $20 a piece, a cheap test.


So I do have springs on all the calipers, and yeah it makes since that it could be part of the problem. But as I've mentioned this issue started at day 1, the springs hadn't been on for very long.


Ok, thanks again for the help. I'll update as I move along. gonna take a while........

[Painter]

Two possibilities-
1- You have to bleed the gauge.
2- If you have moved the attachment point for the brake too far and created too much angle where the push rod enters the mc it will **** the piston and cause this problem.

[Eman]

2) Since I've been swapping lines on the MC, I will thoroughly bleed the brakes again, then as mentioned, remove the lines at the caliper and cap them. Not sure what I will cap them with, but a short flare plug would be great as not to add a lot of air.
Not sure what type lines you have or how they attached to the caliper. If they have flared lines get a line union that fits the flare nut and a plug for the other side. If it's a banjo just use copper washers and a nut and bolt.