Bleeding brake problem.
Stellar HDF Member
Joined: Feb 2013
Posts: 3,072
Likes: 1,726
From: Dallas, Texas
Just had the exact same thing happen to me. On my 1977 XLH 1000 retirement project bike. Rebuilt caliper and master cylinder, resurfaced rotor, NOS front brake line and a new bleeder screw. Had my Wife assist me with her pumping the brake lever but it would not build any pressure. I cracked the brake line to the caliper and she pumped it. After a few pulls, DOT 5 came squirting out. Tighten the caliper fitting, add DOT 5 to the cylinder and pump and bleed. Now DOT 5 squirting out of bleeder. POS. Put the 40 year old mangled bleeder screw back in. That was 1 month ago. With the new ceramic pads, that old Pie Caliper stops as good as my 07 Dyna.
Outstanding HDF Member
Joined: Dec 2012
Posts: 2,557
Likes: 235
From: Texas
When I replaced my handlebars and brake line, I decided to do a complete top-down rebuild. Everything went according to plan until it came to bleeding...I worked for HOURS and could not get all the air out. I tried every trick I know, bleeding from each fitting, vacuum pump, oil can...I was so frustrated that I just walked away and left it for later. I finished up some more things over the next couple of days and came back to the brake issue...and it bled out perfectly and quickly the first try. I did some research and it seems that DOT 5 will trap micro bubbles that can totally muck bleeding up. Accordingly, letting it set for a few days allows the air to collect into bigger bubbles which will bleed out quickly.
I am just a shade tree mechanic and I have had brake issues with my vehicles on many occasions over the years but I have never heard about microbubbles...but then, I have never dealt with DOT 5 either. Whether this microbubbles explanation is true or not, I have since rebuilt two more front systems and did not have a repeat of this problem. No issues with top-down bleeding without any vacuum or speciality tools, just a rag, short piece of tubing, a jar, and a wrench...
But that first time was a ****!
I am just a shade tree mechanic and I have had brake issues with my vehicles on many occasions over the years but I have never heard about microbubbles...but then, I have never dealt with DOT 5 either. Whether this microbubbles explanation is true or not, I have since rebuilt two more front systems and did not have a repeat of this problem. No issues with top-down bleeding without any vacuum or speciality tools, just a rag, short piece of tubing, a jar, and a wrench...
But that first time was a ****!
Seasoned HDF Member
Joined: Jan 2015
Posts: 15,946
Likes: 7,042
From: Sandy Eggo's North County
When I replaced my handlebars and brake line, I decided to do a complete top-down rebuild. Everything went according to plan until it came to bleeding...I worked for HOURS and could not get all the air out. I tried every trick I know, bleeding from each fitting, vacuum pump, oil can...I was so frustrated that I just walked away and left it for later. I finished up some more things over the next couple of days and came back to the brake issue...and it bled out perfectly and quickly the first try. I did some research and it seems that DOT 5 will trap micro bubbles that can totally muck bleeding up. Accordingly, letting it set for a few days allows the air to collect into bigger bubbles which will bleed out quickly.
I am just a shade tree mechanic and I have had brake issues with my vehicles on many occasions over the years but I have never heard about microbubbles...but then, I have never dealt with DOT 5 either. Whether this microbubbles explanation is true or not, I have since rebuilt two more front systems and did not have a repeat of this problem. No issues with top-down bleeding without any vacuum or speciality tools, just a rag, short piece of tubing, a jar, and a wrench...
But that first time was a ****!
I am just a shade tree mechanic and I have had brake issues with my vehicles on many occasions over the years but I have never heard about microbubbles...but then, I have never dealt with DOT 5 either. Whether this microbubbles explanation is true or not, I have since rebuilt two more front systems and did not have a repeat of this problem. No issues with top-down bleeding without any vacuum or speciality tools, just a rag, short piece of tubing, a jar, and a wrench...
But that first time was a ****!
Outstanding HDF Member
Joined: Dec 2012
Posts: 2,557
Likes: 235
From: Texas
I read about that on the interweb back then and tried it...it didn't work either. But when I think about it, the brake system is closed and pressurized to push the pistons when the lever is pulled so there should not be any way for the air to vent out through the master cylinder therefore it seems more logical that leaving the lever in the released position would provide venting back through the master cylinder. At least that is what I experienced recently when the master cylinder vent hole got plugged...the brakes stayed pressurized and the brakes didn't release...
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