Brake = WTF!

[freekstyle]

When I went riding last I had a sudden disappearance front brake. I figured I had moisture in the lines because I used DOT 3 the last time I blead my brakes. I bought some Dot 5 this time and proceeded to bleed the system. After about two or more hours of this I have given up for the night. I tried the normal methed. I tried the gravity methed. I tried to elevate the caliper above the master. I even tried to force air out by using a bottle full of fluid at the caliper. I always get the same results, I pump the brake lever, hold it in, open the bleeder and nothing comes out. I have no resistance in the lever at all untill I get to about 50 pumps, and even then the lever still pulls in all they way. I thought the the master may be bad but it seems to be working fine. If I put my finger over the hole in the resivor and pull the lever it has a ton of force. Also if I open the bleeder first and then pull the brake lever fluid will squirt out fine.

What the hell is going on. There cant be any air left in that line I ran a full bottle of fluid throught it. Something has to be broken some place but I have no idea what or how to check for it.

Please help.

[Matt96xr6]

First off DOT5 is silicone brake fluid. It is not compatible in the DOT 2, 3, 4, & 5.1 brake systems. So now you need to remove all that DOT5. DOT5 is a PIA to bleed as it traps air in tiny bubbles as you pour in the fluid. It takes practice.

Back to problem. Flush the system and use a HiTemp DOT3 fluid. The Castrol LMA is probably the best stuff for the money as it has a very high wet boiling point (what matters, not the dry boiling point). Once you have the correct fluid, bench bleed the MC. Install it on the bike and then you may need crack the banjo bolt at the MC to bleed it a final time. Then start pumping the lever and bleed the caliper. Let it sit for an hour or so, then bleed it one more time. Should get everything out.

If you still have some trapped air, removing the caliper and bleeding it off the bike helps so you can invert the caliper. Or a vaccum bleeder works wonders once you seal the threads on the bleeder.

[yzf450jack]

Flush out your brake system with rubbing alcohol to clean out every thing first

[SureBlue]

Hope this helps: http://mysite.verizon.net/avinh/motorcycles/wr250f/changing_brake_fluids.html

You can also try the old fix to get rid of a soft brake lever feel: pump the lever to create pressure and zipty it to the bar and leave full pressure on the brake for overnight.

[roostmonster]

That was an excellent example of how to bleed your brakes.

[Matt96xr6]

Just an FYI, dry boiling point dont mean squat. Once you open the bottle, the fluid starts absorbing moisture. So the wet boiling point is what you need to look at in a brake fluid.

Most racing cars use a HiTemp DOT3.

HEre is more info on fluids that are common:

http://www.shotimes.com/SHO3brakefluid.html

[freekstyle]

Okay, I put my caliper back on and blead the brakes normally with my son at the lever using the proper fluid and I let it sit for and hour then did it again. Thanks matt96xrs I had no idea the silicone would make a difference. Making this a two person job I found it much easier. I poured a little alcohol in as suggested by yz450jack and then followed the procedure that sureblue posted. After about 20 minutes I got all the blue Dot 5 out as well as the alcohol. It took at leat an hour to get it working close to correct. I have restance in the lever, I can pump it up release the bleeder and the lever will sink in. finally it resembles how a brake should work. All the blue is out of the system and the resivoir is no longer milky. But even after all this I can still pump the lever, hold it and after a few seconds it sinks all the way in. I pumped it up and ziptied it to the bar and Im letting it sit over night as suggested by sureblue. Since I have gone from a complete brake failure to almost working right I am guessing that I dont have any bad componets. I still cant believe what a pain bleeding the front brake is. My son was complaining about his hands and arms hurting from all the pumping, I am looking forward to seeing his face when I tell him tomarrow that he has to help me bleed the brake again.

I am thinking about my rear brake now as I have never changed that fluid. The brake works great but if the front just failed the rear may fail soon as well. I would be up sh*t creek If my rear brake goes out as suddenly as my front did. I am going to take a guess that it wouldnt be as big of a pain because the line runs from front to back unlike the front that runs up and down and catching all the air in the process. Everyone that has posted has offered great advice, THANK YOU.

[flintlock28]

Hey sureBlue; How does this old method work??? I mean what's the concept of what happens with this overnight pressure??

Don

[SureBlue]

Hey sureBlue; How does this old method work??? I mean what's the concept of what happens with this overnight pressure??

Don

Don, I am not sure but it really works if you have a soft feel front brake lever, next morning it is rock hard. I guess it removes small air bubbles from the fluid that cause the soft feel. Maybe grayracer can tell the exact scientific explanation

[flintlock28]

That sounds like a logical explanation....mine is just a little tiny bit squishy, but first I'm going to replace my brake fluid. God knows what the guy ahead of me used on it.

Don

[joker650]

After about 20 minutes I got all the blue Dot 5 out as well as the alcohol. It took at leat an hour to get it working close to correct. I have restance in the lever, I can pump it up release the bleeder and the lever will sink in. finally it resembles how a brake should work. All the blue is out of the system and the resivoir is no longer milky. But even after all this I can still pump the lever, hold it and after a few seconds it sinks all the way in.

I beleave that if you use the DOT-3 in a DOT-5 system all the rubber components will be damaged. The cups and seals swell up and will no longer work properly.

Check into this, this type of damage can really hurt you.... even KILL you.

[SureBlue]

Joker, I was laughing out LOUD when I saw your avatar

[freekstyle]

Actually it was the other way around I put DOT 5 in a DOT 4 system. I am hoping this didnt cause any damage, it was only in the system for overnight.

I did he zipty on the lever thing last night and it did help a lot, however I could still pull the lever back all the way after a 2 to 3 seconds, it just had more resistance. I remember hearing an auto mechanic say that he never pumps the brakes to bleed them, he said he opens the valve then pushes the petal down, closes the valve and releases. He said that if you pump the brakes the increased pressure in the line can cause trapped air to be forced in to the fluid in small bubbles and will be very hard to get out.

Anyone ever hear of this? Also I how do I bench bleed the MC? I didnt know how so I didnt do it and Im thinking now I should have. Last question. How do I know if I have a bad componet? I dont see fluid leaking out from the caliper or line.

BTW, I changed the fluid in my rear brake as posted by surebluse and it was quick and painless (10-15 minutes).

[Matt96xr6]

basically the open MC (lever to the bar) allows the air to travel up into the reservior in theory. WIth any new system, you should bleed it after the first day again. By then the air will have a chance to pool in one place and much easier to get that final air out.

IF you can pull the lever to the bar with normal resistance, you most likely have a tear in the MC seal.

[Pincushion]

You've got a problem. I replaced my MC and brake line recently on the front and it took me less than 20 minutes to bleed the bone dry system.

If your MC is toast then check EBay, I got a brand new CR master cylinder for about $50 not too long ago.

[MisterMan]

When I went riding last I had a sudden disappearance front brake. I figured I had moisture in the lines because I used DOT 3 the last time I blead my brakes. I bought some Dot 5 this time and proceeded to bleed the system. After about two or more hours of this I have given up for the night. I tried the normal methed. I tried the gravity methed. I tried to elevate the caliper above the master. I even tried to force air out by using a bottle full of fluid at the caliper. I always get the same results, I pump the brake lever, hold it in, open the bleeder and nothing comes out. I have no resistance in the lever at all untill I get to about 50 pumps, and even then the lever still pulls in all they way. I thought the the master may be bad but it seems to be working fine. If I put my finger over the hole in the resivor and pull the lever it has a ton of force. Also if I open the bleeder first and then pull the brake lever fluid will squirt out fine.

What the hell is going on. There cant be any air left in that line I ran a full bottle of fluid throught it. Something has to be broken some place but I have no idea what or how to check for it.

Please help.

is your resavour (sp) cap cracked????