Draining Brake Fluid

Discussion in 'Touring Models' started by tencrore, May 22, 2009.

  1. tencrore

    tencrore Member

    I searched in the Self Help section, but could not find specifically what I am looking for, so I thought I would post the question here.

    I am in the process of changing the front brake cables to the "diamondback" braided style and would like to know how to completely drain the front brakes of brake fluid.

    I am thinking I would need some sort of tubing to go over the bleeders so that the brake fluid can drain into a container. If so, can anyone specify the type/size of tubing needed?

    As far as refilling and bleeding, the Self Help section is great. Thanks Glider!!

    Thanks in advance for your help.
  2. kemo

    kemo R.I.P

    3/16 clear tubing should do the trick. Slip the hose over the bleeder and let it drain into a plastic bottle and crack the bleeder open and squeeze the lever or just let it drain out.

    NEWHD74FAN Experienced Member Retired Moderators

    Plenty of different methods, but Kemo' is the simplist...just remember that after you have done the fluid change make sure all the air is purged out by slowly depressing the brake until 2/3 or so and close the bleeder and release. Repeat until you have some firm braking feel.

    Finally, do the overnight thing, just to be sure all air is purged. Bungie cord the lever or foot control actuating the brake allowing the airbubble(s) to rise into the master cylinder. In the morning, use a soft rubber/plastic mallet and gently tap the brake caliper furthest from m/c, then the hoses, crossover fittings and to the m/c. Hold the brakes and remove the cord, gently tapping m/c as you release the brake slowly. Pump brakes slowly several more times while tapping and all the air should be out.

    Always check the brakes for firm feel and bounce bike forward to verify good braking with 1/4 to 1/3 travel before every ride...if spongy or more than 1/2 travel, you still have air in the lines, so you may have to repeat overnight thing over several days.
  4. glider

    glider Veteran Member


    NEWHD74FAN Experienced Member Retired Moderators

    Leave it to Glider to find the good stuff...oh yeah! :newsmile021:
  6. TQuentin1

    TQuentin1 Well-Known Member Staff Member Moderator

    I like the idea of the speed bleeder for the rear brake since the caliper is above the master in that system. On the fronts however, I like to flush the system out with several fills of the master cylinder and THEN push fluid in from the bleeder up to the master filling it that way. There is some discussion of this approach here:

    Bleeding Brakes - Harley Davidson Community


    NEWHD74FAN Experienced Member Retired Moderators

    Rear brakes are tough to bleed especially on my Sportster because the rear hose actually curves above the caliper, drops below the rear swing arm pivot to crossover block, then the hose snakes up to low mounted master cylinder. Plenty of places for the air bubbles to accumulate.

    One man brake bleeding means you do the "YOGA" thing, pressing the brake pedal while fiddling with the bleeder screw/hose (or use a "significant other" to help in the festivities). That one-way bleeder check valve makes sense for the rear. On cars there is a clear tube with check valve available I think from Lisle, I think.
  8. fin_676

    fin_676 Experienced Member Staff Member Moderator Contributor

    Over the years have taught all the family how to assist in brake bleeding but the kids have all left home now wife is always away working and the dog just doesn't get the gist of pumping the brake as i open and close the bleeder have now had to resort to using various devices that use a ball and spring
    on the whole they work fine but prefer that the tubing arcs up wards from the bleeder and always contains fluid
    just fitted extended reach forward controls to 92 softail custom this involved moving the rear brake master cylinder and fitting a longer brake hose so had to drain the whole system
    just take off the banjo fittings and let the fluid flow out
    removed the rear calliper and gave it a good check over popped the piston out by using a wee bit of air from the compressor good clean out and reassemble
    as per normal on these occasions the master cylinder fails to push the fluid through the system (really needs to be primed)
    got the 150ml syringe off the shelf stuck on some plastic tubing
    filled the syringe with dot 5 fitted tubing from syringe to bleeder opened bleeder and forced the brake fluid in till reservoir half full close bleeder used syringe to fill reservoir up to full (no drips no mess)
    forcing the fluid in through the bleeder will draw in a little air so now bleed in the normal way push down brake pedal then open bleeder close bleeder release brake pedal no more bubbles in the fluid is good clean up and have a beer
    using this fill procedure has never let me down takes 15 minuets and the job is a good one took much longer to type this than fill and bleed the back brake