Hello all,

I've searched all the relevant threads, googled the sh*t out of this, tried everything and nothing has worked. The front brake will NOT bleed.

I took on a project for a good friend of mine, another Marine here on Pendleton. We painted the fenders, tank, wheels, fixed blocked PCV passages from a botched Screaming Eagle install...the last thing he wanted was to put 18" apes on his 2002 Fatboy and when I looked into it the project looked like an easy day. I ride a CBR1000, you can burn me for that if you want but I wave at everybody and we've got more in common with each other than we do with the cagers.

After installing the new Magnum brake line I've been trying to bleed the front brake and I've had no luck. I'm an ASE Certified Master Technician, this isn't new to me but this one is wrecking my life right now.


Here's what I've done:

• I've taken the MC apart to clean and inspect, seals are good and cylinder and piston are clean with no corrosion. Passages from the reservoir into the cylinder are not clogged.

• Bench bled the MC, I'm able to get all the air out.

• I can get a little fluid down into the caliper with a Mityvac but it draws a 20" vacuum and only very slowly pulls frothy fluid out of the caliper. Taped the threads to eliminate air leakage around the bleeder.

• As per service manual, tried the "crack the bleeder-squeeze-tighten bleeder-release" method but no matter how slowly I release the brake handle or how many seconds/minutes I wait before I crack the bleeder again it always leaves the system under a vacuum and just draws air back into the caliper.

• As per service manual I fashioned a back-bleeder to push the fluid up into the reservoir from the caliper and I'm not able to move ANY fluid into the system.

• I am unable to gravity bleed the system because with the cap removed NO fluid will flow down into the hose from the MC.

Here's what I've observed:

• When bench bleeding the MC once I've short-stroked all the air out of the cylinder when I push the piston all the way in and put my finger over the fitting where the banjo bolt goes, when I release the piston it'll draw a strong vacuum on my finger that will not subside. It does not refill the cylinder from the reservoir.

• When bench bleeding the MC I can get all the air out, with the cap off fluid will still not flow from the reservoir. Not a drop.

• The MC has markings that say 9/16". From my research I understand that for some single-caliper front brake systems they may have used 9/16" or 5/8" MC's. Is it possible that somebody rebuilt this MC with a 5/8" cup seal that is too tight?

• The Magnum line came with copper crush washers, not the steel/rubber ones that I removed with the old line.

• The parts place sold him purple DOT5 fluid, I read somewhere that I might should be using something different? The old crappy fluid did not have a purple hue.

Right now I'm blaming the MC for stopping the flow of fluid. I had a half a mind to take a tiny drill bit and enlarge the orifice closest to the banjo fitting. It seems to me like the fluid is too viscous to make it through that hole.


Again, it's a 2002 Fatboy, purchased used from a Harley dealer about 6 months ago.


I beat my head against the wall for 8 hours today trying every suggestion I could find on previous posts from all HD forums...even the ones that made no sense to me what-so-ever.

I would really love to be done with the project so my buddy can get back on the road and I can get back to my own dang projects!

 

What you have done seems OK but check with HD (or user manual) to make sure the bike uses DOT5 brake fluid. My 1996 Heritage does but my 09SERG uses DOT3. DOT 3 and 5 are not compatible, if the system is not cleaned and flushed (brake system cleaner) properly apparently a sludge can form from the reaction of the different fluids; maybe this could be causing the problem (sounds like a blockage somewhere).

If not try taking the brake line off the caliper and bleed the MC and line using the Mityvac pump to pull the fluid through; as well, try flushing the caliper leaving it full of fluid before re-attaching the brake line to do a standard brake bleed until no air bubbles. Good Luck

 

I don't understand all the different uses of brake fluid. When I bought my '06,I was all set to buy dot 5,which my '93 Classic used. luckily,I noticed that the master cylinder cap specifies dot 4. As I remember,seems like the factory went from dot3 to dot5,then dot4.
I don't think any are compatible with the others,and wouldn't want to mix them to find out.

 

If the brakes were ok with the old brake lines then it sounds like a blockage somewhere there, possibly a bad banjo fitting at the master cylinder.

 

I wouldn't use any tape to seal. It should be fine without it.
back filling is what I do using a bleeder suction pump.

 

Loosen the banjo bolt on the MC, get a big syringe and a short peice of tight fitting clear hose, push the fluid into the bleeder 'till it comes out the banjo bolt, tighten the bolt and continue to push though the mc.

Of coarse close the bleeder and make sure you don't inject air if you have to refill the syringe.

 

02 is DOT 5. It will say right on the cover for the master cylinder.

 

On my 2002 Fatboy, the only way I could bleed the brakes was to pump up the MityVac to about 30 lbs and THEN open the bleeder. Just be sure to close the bleeder while there is still pressure in the line.

Another tip: If the brake pedal/lever still feels mushy after bleeding, try pumping the brake a couple time then wrap a bungee cord around the lever and grip to keep pressure on the lever. Leave the bungee cord over night. Doing this forces all the air bubbles into the MC and the result is a firm brake lever.

 

frothy = leak in system
have you tried applying vacuum at the caliper bleeder while the cap is loose and slowly applying brake lever pressure?
From your description it sounds like the m/c is not allowing fluid to the lines.

 

Have you cleaned your caliper pistons. That can screw up the bleeding process.