QuestionI have a Harley Softail but I feel brakes are brakes and you can possibly help me. My front braking system isn't holding pressure. At first HD assumed it was a faulty front master cylinder. They replaced my aftermarket master cylinder with a factory model and I also gave them a new caliper and it still loses pressure. So at this point the front braking system is still losing pressure with both new and old calipers and with both new and old master cylinders. I suggested its a faulty brake line or perhaps the fitting on the brake lines are possibly warped or maybe washers are missing. They dont know how to fix it? Truthfully I never heard a dealer say such a thing. Have any ideas?
AnswerHi Alex,
I work on HD's, too. You're right...brakes are brakes, bearings-r-bearings, etc...
It's possible that a hose or fitting is defective. If so, there will be evidence of brake fluid on and around the defective part. The part cannot draw air without losing fluid.
I suspect air remains in the system because it is not thoroughly bled. Other causes may exist, too. See the tech files below. I return tech files via email. There was no email addy with your question as requested. I've pasted these for your convenience
Respectfully,
Mark Shively
Brake Doesn't Hold
Disc brake:
Air in the brake line
Pad or disk worn
Brake fluid leak
Disc warped
Contaminated pad
Brake fluid deteriorated
Primary or secondary cup damaged
Master cylinder scratched inside
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Brake Bleeding 101
By Mark Shively
Use high quality DOT 4 brake fluid (or preferred type) from a sealed container. Remove the old fluid from the master cylinder reservoir. Use a cooking type squeeze bulb baster to remove the bulk of the fluid. Use a paper towel to remove any remaining fluid. Top off the empty reservoir. Top them off periodically during this procedure. Do not spill any fluid on your bike because it may damage the paint. The front brake reservoir tends to spit fluid out the top during this process so make sure you place a bunch of rags, old blankets, or towels over the fuel tank.
You can make a bleeder drain container fairly easily by taking a plastic container with a screw on lid. Put a hole in the container lid just large enough to get the hose through. Put a short section of hose on the bleed valve on the brake caliper. Put the drain container on the other end to catch the runoff. You'll need to move the hose and container around to each caliper as you work, or use more than one container.
Use a wrench to open the bleed valve while simultaneously squeezing the lever (or pedal). About 2/3 of a turn on the wrench will do it. Fluid should run out of the hose at this time. When you squeeze to within 3/4 of your full lever pull, use the wrench to close the bleeder valve. It is important that you close the valve before hitting full travel on the lever. Release the lever and repeat the process (squeeze lever, open valve, close valve, release lever) until the fluid runs with no bubbles and the lever is firm. You'll be amazed how firm you can get your system.
While this way will work and there is absolutely nothing wrong with it, it is a big misconception that you have to shut the bleeder valve between every pump/squeeze of the lever. People do this on their cars, too. Pump, Open/Close; Pump, Open/Close…. You really don't need to do this. As long as you've got fluid flowing through the bleeder tube, you can just keep pumping/squeezing the lever until fresh brake fluids runs through the system. The end result is a flushed and bled system. Just make sure the reservoir stays topped off. If you bleed it dry, you'll have to start all over again.
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Brake/Clutch Bleeding 102
By Mark Shively
Vacuum bleeders sometimes are more troublesome than efficient. Other times they work well. The old school way to bleed is to allow the master cylinder to purge the system of air. This may be slow at times, but effective.
To begin, flush the existing brake/clutch fluid from the reservoir. Pump it through the lines to the bleeder valves. Flush thoroughly until you see new fluid exit each valve. Start with the closest bleeder valve and work away from the master cylinder, to the next furthest valve.
To flush, pump the lever a few times and hold the lever in as if bleeding the line. Open the bleeder valve wide open and leave it open. Begin pumping until you see fresh fluid at the bleeder. When you see fresh fluid, hold the lever in on the last pump and tighten the valve. Pump the lever and crack the valve for a quick bleed. Repeat for all bleeders. You may not need to bleed the system after the last valve is flushed.
If bleeding is necessary, bleed the system by starting with the furthest bleeder valve and work towards the master cylinder (just the opposite of flushing).
If master cylinder needs purged of air (rare) do the following: adjust the master cylinder so it is as level as possible on the handlebar. Remove the reservoir cap and top off fluid to proper level. Very, very, slowly pull the brake lever in while monitoring the inlet/outlet ports in the bottom of the reservoir (machined holes). Release the lever slowly, alternating lever pulls of about 1-2mm, and full pulls. The shorter pulls seem to purge air best. Look for air bubbles to rise from the ports. Repeat until no air is seen and/or lever feels firm.
If no air is seen, pull the lever in and let it return quickly by releasing it from your fingertips. It should snap back under the tension of the plunger spring. Repeat this several times while watching for air bubbles. Switch between the two methods described above: slow short pull method and long quick release method.
When no air is observed, the master cylinder is purged of air. Be patient, this may take several minutes. If no air is observed and “brake” lever feels soft, bleed lines until lever feels firm. Clutch levers should feel soft. Synthetic brake fluids may result with a softer than normal lever feel. Old rubber brake hose may result with a softer feeling lever due to expansion of the hose from age. For best results, use braided steel brake lines and DOT 3 or 4 brake fluids.
Tip: Shake or gently tap brake hoses with a tool to send residual air up the lines to the master cylinder.
Note: Clutch levers are not intended not pump-up to a firm feel.
