Replacing the brake pads front and rear on one of my bikes. Should the brake system be flushed and new brake fluid added or just go with whats in there? Dont know if this is even necessary but I wonder if the fluid that is in there now is what was put in when it left York, PA 10 years ago? Is flushing a normal part of this maintenance? I doubt the Dealer has ever done this when I have had them replace the pads.

 

well to be safe why not i do it every 7500 miles or so or if we have a perticular cold winter its a safety item you need to stay on top of it

 

Not that hard to do..Put a clear tube on the bleeder valve into a jar with
some clean fluid in the bottom.Start pumping...and add new fluid to the reservoir
as you go. Be careful to not let the fluid level get to low. Continue till the fluid runs clear.Whatever you do....don't get any on your paint

 

Rustell,

My assumption is that I should connect the tube to the bleeder valves and pump the brakes to completely drain out the "old" fluid then open the reservoirs and fill with new fluid, pumping the brakes until fluid comes back thru the bleeder valves. Why clean fluid in the jar? The fluid is not coming back into the system from the jar is it? I know about what brake fluid does to paint (dont ask me how I know). thanks

guess I could

 

You do not want to pump out the old fluid and then start the new fluid.

If you do that you will fill the system with air and you will have do do a lot more work to pump all the air out of the system.

Remove the reservoir cap and start pumping out the old fluid. Refill the reservoir with new fluid as needed to prevent it from going too low and sucking air into the system.

Keep pumping the fluid through until you see clean fluid coming out. If you have two calipers on the front wheel do one until clean fluid comes out and then do the other. The second will not take as long as you will have already purged part of the system. Close everything up and clean up the mess and you're done.

There are a number of ways to flush the fluid including the old apply brakes/open bleeder/shut bleeder/release brakes method. This works but can be awkward unless you have really long arms or have someone to help. Vacuum systems that pull the fluid through the open bleeder are popular because you do not have to pump the lever. You still have to watch the level in the reservoir so it does not run dry.

I have tried a couple different vacuum systems and could not get them to work to my satisfaction. The ones I tried pulled air through the threads of the bleeder more than they pulled fluid through the system. There is a good chance I was not doing something correctly but I do not know what it was.

On my last two bikes including my current one I installed Speed Bleeders. These bleeders replace the factory bleeder valves. They have a one-way check valve inside. To use, you open them about a quarter turn, attach a tube and collection bag or bottle, and simply pump the brakes. The one-way valve prevents air from entering the system. Everything else works the same (pump until you see clean fluid, keep the reservoir full). I bought the stainless steel versions and I think they were $10 or $15 each. My bike took three, two on the front and one on the back. With these installed I can easily and quickly flush the brake fluid by myself.

You can order Speed Bleeders directly from the company (do a search for their web site) or from various distributors.

I am not sure what your manual states on the brake fluid change frequency but for most vehicles it is once every two years regardless of mileage. The reason for the two years interval is because standard type 4 fluid can absorb moisture, whether being ridden or not.

I hope the helps.

 

I do this every other year but may go to annual flushing. I use a big plastic syringe that came in my wifes set-it-and-forget-it cooker. I attach a small length of plastic hose on to the bleeder and draw it out with the syringe. Good post and something we should be doing regularly.

 

Thanks guys! Yep, forgot about allowing air into the system, hence Rustell's comments about having fluid in the collection jar....keeps the system "closed". Have thought about those speed bleeders, will check that out. Again, many thanks for the simple instructions. I see now the reason to change fluids...ie moisture buildup. Now...onto the real work of getting this done....getting warmer here and want to get out and ride!

 

FWIW, the Softail owners manual for my '08 says to change and flush the brake fluid every 2 years.

 

Should change fluid every 2-3 years. Be sure what fluid your bike has in it, probably DOT 5 which isn't very common any more. If so only use it. For instance DOT 5.1 is incompatible.

 

IMHO this is the best reply. short concise and correct!

The reason you change brake fluid periodically is that Brake Fluid is Hygroscopic . . . that means that it attracts and holds water from the air.

Water in your brakes is a BAD thing and it creates two main problems: 1.) Water is good for corrosion which is NOT good for the insides of Brake Hydraulic Systems. and 2.) Water boils at roughly 212 F. Unlike DOT 4 Brake Fluid (Which is what Harley-Davidson specifies) boils at 446 F, or more than twice what water boils at. Since Brakes get much hotter than 212 F boiling water is NOT good to have in a Brake system. When the water boils, and turns into steam (which takes up far more room than the liquid water) it will push all or most of the Brake Fluid out of the Caliper and back into the Master Cylinder . . . the next time you go to hit your brakes . . . there are no brakes. This is because there is no (or very little) Brake Fluid in the Brake Circuit. BTW this is also why you should use a "New" can of Brake Fluid every time you do this . . . that old can? Guess what it's got dissolved in it after sitting around (even with the cap on) for a while?