I finished bleeding and changing the brake fluid on the front calipers but the brake lever feels really spongy. It was much firmer before I changed the fluid. I own a MityVac vacuum bleeder and I was careful to keep topping off the reservoir so I wouldn't let any air into the lines. I did the left caliper first and then the right caliper.
So why is the feel still spongy? I can't see how air might be getting into the system. I already went through two small bottles of brake fluid.
When I hook up the MityVac and open the valve on the caliper, brake fluid and air is coming out. I thought this air was leaking into the MitvVac tube from around the bleed nipple (which I hear is a common occurrence), but now I'm not so sure. Here's a video.
How is air getting in if I keep topping off the reservoir before it gets low? Or do I just need to ride it around the block to let it "bed in"?
Most likely you are getting air in around the threads of bleed nipples (heh-heh-heh, he said nipples......)
Unscrew them, don't worry you all ready have air in there just don't touch the lever, and wrap some teflon tape around the threads and reinsert. Again with the mity-vac, do a bleed and you should be firm (heh-heh-heh, he said firm) in no time at all. :dry: :rolleyes:
[image: View Post]vchengap, on May 16 2009, 01:08 AM, said:
I finished bleeding and changing the brake fluid on the front calipers but the brake lever feels really spongy. It was much firmer before I changed the fluid. I own a MityVac vacuum bleeder and I was careful to keep topping off the reservoir so I wouldn't let any air into the lines. I did the left caliper first and then the right caliper.
So why is the feel still spongy? I can't see how air might be getting into the system. I already went through two small bottles of brake fluid.
When I hook up the MityVac and open the valve on the caliper, brake fluid and air is coming out. I thought this air was leaking into the MitvVac tube from around the bleed nipple (which I hear is a common occurrence), but now I'm not so sure. Here's a video.
How is air getting in if I keep topping off the reservoir before it gets low? Or do I just need to ride it around the block to let it "bed in"?
You definitely still have air in those lines. Despite pulling all that fluid through the lines, air bubbles will still tend to stick and stay in the lines and the banjo fittings.
Use the handle of a big screwdriver and gently tap the brake lines through its whole legnth, working your way up from the caliper body to the top banjo fitting at the lever. Do this numerous times and also flick the lever many times so it snaps back and this will knock loose many very small bubbles still in the lines. You will actually see a small stream of bubbles coming from the bottom hole in the fuild reservoir. Do all this repeatedly till you cannot see any more bubbles coming up, then you will have a properly bled brake or clutch system, devoid of any air bubbles that causes the spongey feel.
both good answers. the video is showing air drawn in around the threads probably. teflon works better, but mine still do it even thought the bleed just fine. you might want to crack the top banjo bolt open to bleed the top. this usually is where the bubles hide. make sure and wrap around the area with lots of rags to keep the fluid off the bike....VERY bad for the paint
[image: View Post]turtlecreek, on May 15 2009, 09:28 PM, said:
things change with the linked brake system.
He has a 4gen so no LBS.
+1 on no probs using a mityvac, great reduces the time to change out fluid although not necessary when bleeding.
Oh yeah, another thing. Binding the brake lever overnight with a zip tie or similar can give a nice firm lever in the morning (must resist another bad joke)....
[image: View Post]FotoMoto, on May 15 2009, 08:18 PM, said:
Most likely you are getting air in around the threads of bleed nipples (heh-heh-heh, he said nipples......)
Unscrew them, don't worry you all ready have air in there just don't touch the lever, and wrap some teflon tape around the threads and reinsert. Again with the mity-vac, do a bleed and you should be firm (heh-heh-heh, he said firm) in no time at all. :dry: :lurk:
I'm sure Teflon tape would work, but I just smeared heavy grease around the base of the nipples before putting the MityVac hose on. It kept air from being drawn in when the the nipples were opened up (after vacuum was applied). Learned that trick on an auto forum a while back. Worked like a champ and was easy to wipe off when done.