how do you put brake fluid in brake line and caliper?
- Thread starter blarf
- Start date
oldguy
Always Broken
- Dec 26, 1999
- 9,419
- 0
When I do it I always start filling from the bleeder valve and reverse fill/bleed the system. I made my own bleeder from a large hypodermic needle (like the ones used on farms) that holds about 100cc. I attached a tube that is the same size as the bleeder nipple to the part where the needle would normally be. I fill the hypodermic with fluid, place the tube over the nipple, open the valve and pump the fluid in then close the valve. Repeat until the reservoir is full and then replace the cover. Next step isn't required but will firm the lever up- pump the lever to set the pads against the rotor and while the lever is squeezed use zipties to hold it in and leave it overnight.
If you go from the top, you sometimes have to put some backpressure on the system to get it to pump. I will open the bleed screw and place a finger over the hole in the bleeder and pump the lever. Let a little bit of air escape each time until you get fluid. Once there is fluid, proceed with a normal bleeding procedure. This method takes a little patience and finess at times. I guess you could bench bleed it like you would a car master cylinder, but this method works ok.
- Thread starter
- #5
well, i got the mityvac to try to fill up the front bake. fluid is going through (i almost filled up 3/4 of the bottle of the mityvac) but i do NOT get any pressure from the brake. lever goes all the way in and wheel spins freely. what am i doin wrong??
Now that you've got fluid in the system, you've got to bleed it. I pull the lever, crack the bleed screw slightly, before the lever bottoms out, close the bleed screw. If you have hose, slip it over the nipple, route it upwards a few inches before it goes down and into a container. This way, you can just keep pumping without having to close the bleed screw every time. The fluid that remains in the hose will prevent air from being sucked back in.
I done both my brakes yesterday, on each brake I drained the fluid by constantly pumping fluid through the system using the brake lever, whilst topping up the reservoir at the same time. Once I was confident that all fluid had been changed I then proceeded to bleed the system. I make sure that the reservoir is filled right to the top, place a clear piece of tubing over the bleed nipple with the other end submerged into a jar with brake fluid already in it. I pump the brake lever until resistance has built up and whilst holding the brake lever down I then open up the bleed nipple half a turn until fluid/air comes out, then I close it again and release the lever. I repeat this process until all of the air has escaped the system and the brake lever feels solid. If it doesn't feel solid then you either have a massive air trap in the system or a leak.
I would say so yes. The front brake seemed to be harder to bleed than the rear, so all just done really quick pumps with the bleed valve open and eventually the fluid started to flow. You'll figure it out, there's not much to the braking components of a bike so what else could it be???
rmc_olderthandirt
~SPONSOR~
- Apr 18, 2006
- 1,533
- 8
blarf:
the "mighty vac" should be able to bleed the brakes without any additional steps. If you have drawn a significant amount of fluid through (which is sounds like you have) then it should be fine.
If you aren't getting any brake action, then something is wrong.
First question: Once you sucked the fluid through, did you close the bleeder nipple? That little fitting that you put the hose on for the Mighty Vac is also a valve. You open it (turn it counter clockwise) to allow brake fluid to escape. Close it (clockwise) to seal it off.
It is important that you don't allow any air back in the bleed nipple before you close it. You should be able to twist it closed with the hose still attached. It is also important that you keep the master cylinder reservoir full so that you don't suck more air in.
If you have fluid through the system, the bleed nipple is closed and you have no brake action at all then I would guess that you didn't assemble the master cylinder properly. Did you rebuild your master cylinder, or buy an entire new unit?
Just in case the Mighty Vac approach isn't working for some reason, here is the way I recommend to go about bleeding the brakes. Note that this may require two people:
0) Attach a clear hose to the bleeder nipple, route the free end into a can/jar. Note, you may want to loosen the nipple first, and then leave the box end of the wrench trapped on the nipple by the hose.
1) Make sure the reservoir is full.
2) Squeeze the brake lever, hold it
3) open the bleeder nipple. You should see fluid and/or air move through your hose.
4) close the bleeder nipple.
5) release the brake lever.
Repeat steps 1-5 a bunch. As you make progress the feel of the brake lever should improve each pass. You should also be able to see any air bubbles pass through the clear hose. On a car, the reservoir is large enough that you can make several passes before refilling but the reserovior on a bike is often so small that you should refill each time. If you allow the reservoir to run empty and get more air in the system you will have just wasted your time and brake fluid.
When you are done, snug up the bleeder nipple. They don't need to be "tight" and if you over tighen them you can easily break them off and that can be a real bitch!
Rod
the "mighty vac" should be able to bleed the brakes without any additional steps. If you have drawn a significant amount of fluid through (which is sounds like you have) then it should be fine.
If you aren't getting any brake action, then something is wrong.
First question: Once you sucked the fluid through, did you close the bleeder nipple? That little fitting that you put the hose on for the Mighty Vac is also a valve. You open it (turn it counter clockwise) to allow brake fluid to escape. Close it (clockwise) to seal it off.
It is important that you don't allow any air back in the bleed nipple before you close it. You should be able to twist it closed with the hose still attached. It is also important that you keep the master cylinder reservoir full so that you don't suck more air in.
If you have fluid through the system, the bleed nipple is closed and you have no brake action at all then I would guess that you didn't assemble the master cylinder properly. Did you rebuild your master cylinder, or buy an entire new unit?
Just in case the Mighty Vac approach isn't working for some reason, here is the way I recommend to go about bleeding the brakes. Note that this may require two people:
0) Attach a clear hose to the bleeder nipple, route the free end into a can/jar. Note, you may want to loosen the nipple first, and then leave the box end of the wrench trapped on the nipple by the hose.
1) Make sure the reservoir is full.
2) Squeeze the brake lever, hold it
3) open the bleeder nipple. You should see fluid and/or air move through your hose.
4) close the bleeder nipple.
5) release the brake lever.
Repeat steps 1-5 a bunch. As you make progress the feel of the brake lever should improve each pass. You should also be able to see any air bubbles pass through the clear hose. On a car, the reservoir is large enough that you can make several passes before refilling but the reserovior on a bike is often so small that you should refill each time. If you allow the reservoir to run empty and get more air in the system you will have just wasted your time and brake fluid.
When you are done, snug up the bleeder nipple. They don't need to be "tight" and if you over tighen them you can easily break them off and that can be a real bitch!
Rod
- Thread starter
- #11
rod:
i bought the master cylinder kit, 2 pistons, new boots, new seals.... i used my shop manual in order to rebuild/put everything back together. mayby i messed up somewhere, i guess i'll take everything apart and go from scratch again.
i'll check everything you told me tonight when i get back from work
i bought the master cylinder kit, 2 pistons, new boots, new seals.... i used my shop manual in order to rebuild/put everything back together. mayby i messed up somewhere, i guess i'll take everything apart and go from scratch again.
i'll check everything you told me tonight when i get back from work
- Thread starter
- #12
ok , i bought a serynge and injected more fluid through the bleed nipple. brake lever was rock hard but wheel was stuck so i started the bleeding routine. now my lever is still kinda soft (little resistance) but at least my wheel stop hard whenever i hit the brake. how hard should the lever be anyways?
when i spin the wheel, it doesn't spin freely, brake pads are rubbing, is it normal?
when i spin the wheel, it doesn't spin freely, brake pads are rubbing, is it normal?
