Brake Fluid Contamination

Discussion in 'Dyna Models' started by Nuke99, Oct 15, 2010.

  1. Nuke99

    Nuke99 Member

    I could use some advice on brake fluid changeout. I took my 2008 Wide Glide to my local dealer to have a free 56 point inspection conducted. The service department said the brake fluid was contaminated with water at 4%. They said 2% is maximum. I am not sure how they determine that, but the cost to correct is $100. The bike has only 2500 miles on it and is always parked inside my garage when not out on sunny days. Does anyone have experience with brake fluid contamination or how it can occur? Is it necessary to change out the brake fluid? :(
  2. Jack Klarich

    Jack Klarich Expert Member

    Unless they used a Brake fluid Shark made by Mac Tools, how would they know this? Brake fluid will take on moisture it is a hydroscopic fluid. Heat and cool cycles will produce moisture, if you have doubts you can flush your own fluid just remember to use the correct fluid for your bike. :s
  3. kemo

    kemo R.I.P

    Brake fluid is hygroscopic, which means that it absorbs water and that is how it gets contaminated. The cure is to flush out the old and replace with new and bleed the brake system. The higher percentage of contamination means that the brake fluid will boil at a lower temperature. Also the moisture will cause rust in the calipers and master cylinder. The free checkups are meant to do one thing and that is to drum up business in the shop. You should start to learn about your bike. Buy a bottle of brake fluid for $10. and see if a buddy can help you out. Bleeding brakes is not rocket science. Check the self help section out.
  4. fin_676

    fin_676 Experienced Member Staff Member Moderator Contributor

    It is normal service practise with any vehicle to replace the brake fluid every 2 years
    As jack has stated brake fluid is hygroscopic in other words it will absorb moisture there is always moisture in the air as you use the brakes they get very hot the dot rating of brake fluid determines the heat at which the brake fluid will boil however the moisture in the brake fluid will boil at a much lower heat and turn to steam which will compress and the brakes at best will become spongy at worst wont brake

  5. Nuke99

    Nuke99 Member

    Thanks to all of you for your replies. I will change out the fluid myself. I appreciate the information. I also have an Ultra that will probably need the same attention.
  6. Jack Klarich

    Jack Klarich Expert Member

    Remember once you open a can of brake fluid the clock is ticking so to speak, as it will start to take on moisture, buy only what you need, Capital Jack:s
  7. PetieJ

    PetieJ Member

    Whether we like it or not, water is everywhere and finds its way into everything. That’s just the nature of the beast. Even a brand-new sealed brake system will eventually absorb water given enough time.

    The magic of diffusion allows moisture in the air to permeate microscopic pores in the rubber brake hoses and the various rubber seals in the hydraulic system. Sadly, there is nothing we can do about it and if left unchecked the water would sit in our brake system and rot it away from the inside out.

    Hence the need for brake fluid to absorb this unwanted house guest. Because brake fluid absorbs water into solution, the local concentration levels are typically low enough that corrosion is slowed dramatically. As an added benefit, when exposed to low temperatures, the solution state prevents the water from pooling and freezing on its own. While water in brake fluid will certainly increase the solution viscosity at low temperatures, this is much more desirable than having little chunks of ice plugging up the system!

    The next time you are bleeding your brakes to remove the water-contaminated fluid, don’t curse at the brake fluid gods too loudly. After all, the fluid was only doing a job no other fluid can.

    Boiling point of fluid with water % :
    Dry BP (F)@ 0.0% H2O 446 509
    Wet BP (F)@ 3.7% H2O 311 356
    Chemical Composition Glycol Ether /Borate Ester Silicone Based
  8. TQuentin1

    TQuentin1 Well-Known Member Staff Member Moderator

    Be sure you know WHAT is in your bikes' brake systems now, and what is SUPPOSED to be in there. Your brake system is not something to guess at. If you don't know what is in it, start from scratch. If you are even a little unsure, the safest thing to do is to COMPLETELY disassemble the brake system, clean out everything including the lines, chase/clean with alcohol, and blow them out with dry air. Reassemble everything using fresh brake fluid as the oring lubricant for assembly. Make sure it is the right fluid for THAT bike's brake system. Bleed the brakes using the method you like the best (I like to go from the bleeder valves to the reservoir on the front, and from the reservoir to the bleeder valve on the back, and use a vacuum bleeder on the back if you have one). Both my bikes use DOT 5 fluid which is silicone based - NOT compatible with DOT 3, 4 OR 5.1!! DOT 5 is not hydroscopic or at least not like glycol based fluids are. AND, DOT 5 is NOT compatible with the other fluids (notice I repeated this!!!).

    This is one of the most important systems on your bike. Don't mess around. Do it right. If your fuel system or your ignition system doesn't work, the engine may not start or run right; if your suspension system messes up, you may not like the ride; if your brake system malfunctions ... well you get the message!!

    Last edited: Oct 15, 2010
  9. Hoople

    Hoople Account Removed

    Great info indeed. I never realized how important brake fluid maintenance really is. It seems like a good flush every couple of years will do it..
    The front reservoir is easy to get at but the rear on my bike looks like a bear.
  10. NEWHD74FAN

    NEWHD74FAN Experienced Member Retired Moderators

    TQ and Fin_676 have you covered regarding proper brake fluid maintenance and reasons for changing. I usually use an old turkey baster to pull most of the fluid out of the master cylinder, then fill with new fresh fluid, and then flush the lines and bleed system as the final step when done.