brake fluid bleeding problems

[rajoana]

Hi guys,
            recently attempted to bleed by rear brakes, had some problem.

            there were tiny bubbles coming out non stop. realized the bleeding screw has some free play. So i went to get both of them changed.


even after changing the bleeding screws the problem of tiny bubbles appearing does not go away. Because even after changing the bleeding screws there is free play.


So Seems like the thread on the caliper or worn out or something like that.


Instead of changing the whole caliper any economical way of solving thing?

[sinto]

Is it possible that the threads are goosed?
Try araldite

http://www.amazon.co.uk/s/?ie=UTF8&keywords=rapid+araldite&tag=hydrukspg-21&index=aps&hvadid=25376465367&hvpos=1t1&hvexid=&hvnetw=g&hvrand=18059465401194045981&hvpone=&hvptwo=&hvqmt=b&hvdev=m&ref=pd_sl_i5p7ykhij_b

[crickleymal]

Try some PTFE tape on the threads.

[rajoana]

thanks for the reply guys. This forums seems really active.


well ones i have tighten the screw its fine. I guess so no sign of leakage or anything.


the problem is while bleeding. So i guess instead of these sealants or tapes need to do something about the thread.


or were u guys suggesting that these could help while the bleeding screw is slightly loosen for bleeding?

[riedrider]

Try some PTFE tape on the threads.

This would be also my first recommendation. Wrap it around the thread of the bleeder nipple.
Or apply some ATE brake grease (common in Germany) or red rubber grease around the thread.

[rajoana]

ok will give that a try. thanks again. will keep u guys posted if it works.

[maxzer1500]

Only open bleed screw as far as it needs to be to pass fluid, it might only be half a turn and you might feel a lot of pressure at the pedal to achieve this. Even if it's a one way bleed tube i always nip up the screw ( just enough, not fully ) while the pedal is still moving.

[fazersharp]

Only open bleed screw as far as it needs to be to pass fluid, it might only be half a turn and you might feel a lot of pressure at the pedal to achieve this. Even if it's a one way bleed tube i always nip up the screw ( just enough, not fully ) while the pedal is still moving.

That sounds good advice
I had exactly the same issue when I did my front so I gave up in the end and tightened hopfully not too much ( was quite tight in the end ) and then it stopped

[Punkstig]

As with max- sounds like you're opening the bleed screw too much!

[Deefer666]

take your bleed pipe and did the end that you put on the bleed nipple in grease.... No attempt it again if no bubbles then it was an air leak between the bleed nipple and the pipe.

[rajoana]

Only open bleed screw as far as it needs to be to pass fluid, it might only be half a turn and you might feel a lot of pressure at the pedal to achieve this. Even if it's a one way bleed tube i always nip up the screw ( just enough, not fully ) while the pedal is still moving.

ok i have just tried this. No tiny air bubbles spotted. however still have that spongy feeling and bitting is just not enough no matter how hard i step the brake pedal.


could be the pump?

[rajoana]

was read through some other posts here abt rear caliper seizure is a common prob.


If yar piston in the caliper has seized what wld be the symtoms?


no braking at all?


or not enough bitting power like what i m experiencing.

[sinto]

I would take off the caliper, leaving the pads in place and try pressing the brakes, if your pistons are ok they will push together then insert a flat object between the pads and push them back to allow you get them back over the disc, you might have to do this a few times to get them to work loose, then if that's working ok you can eliminate the pistons etc but I'm thinking they will be stuck and will need an overhaul

And if that is the case, you'll want to read this thread
http://foc-u.co.uk/index.php/topic,16810.0.html

[rajoana]

I would take off the caliper, leaving the pads in place and try pressing the brakes, if your pistons are ok they will push together then insert a flat object between the pads and push them back to allow you get them back over the disc, you might have to do this a few times to get them to work loose, then if that's working ok you can eliminate the pistons etc but I'm thinking they will be stuck and will need an overhaul

And if that is the case, you'll want to read this thread
http://foc-u.co.uk/index.php/topic,16810.0.html

right thanks for sharing. will try what said as well.

[Jules-C]

If you have removed the brake caliper it's quite common to end up with a bubble where the brake pipe comes out the top on the master cylinder and depending on the size of the bubble it can be almost impossible to get rid of by normal bleeding since it keeps returning the this high point in the system.  Sometime slackening the banjo bolt on the top the the master cylinder can let the bubble out but you risk letting more air in. 

If you unbolt the caliper from the bracket and the brake pipe guide from the swinging arm and tie it so brake pipe runs uphill from the master cylinder to the caliper and then bleed it you should get rid of the bubble.

[rajoana]

If you have removed the brake caliper it's quite common to end up with a bubble where the brake pipe comes out the top on the master cylinder and depending on the size of the bubble it can be almost impossible to get rid of by normal bleeding since it keeps returning the this high point in the system.  Sometime slackening the banjo bolt on the top the the master cylinder can let the bubble out but you risk letting more air in. 

If you unbolt the caliper from the bracket and the brake pipe guide from the swinging arm and tie it so brake pipe runs uphill from the master cylinder to the caliper and then bleed it you should get rid of the bubble.

Was abt to try this. Seems like the nut at the master pump is locked after putting on much more force the whole bracket broke instead.

[Jules-C]

That doesn't help.  Second hand footrest brackets are usually easy to find on fleabay etc.  It must've been really tight unless bracket already starting to crack after bike been dropped at some time.

[rajoana]

That doesn't help.  Second hand footrest brackets are usually easy to find on fleabay etc.  It must've been really tight unless bracket already starting to crack after bike been dropped at some time.

nah its really tight i have used all my body weight to loosen it.


anyways got the new bracket already. more work to do. guess will try WD 40 n hope it opens up.


1 thing i learn. If it doesn't open with a desend amt of force dun push it further.

[sinto]

nah its really tight i have used all my body weight to loosen it.


anyways got the new bracket already. more work to do. guess will try WD 40 n hope it opens up.


1 thing i learn. If it doesn't open with a desend amt of force dun push it further.

Have you tried tightening it more? (Just a small amount though) then try turning it left to loosen it??

failing that, a bit of heat may help you.

[rajoana]

nah its really tight i have used all my body weight to loosen it.


anyways got the new bracket already. more work to do. guess will try WD 40 n hope it opens up.


1 thing i learn. If it doesn't open with a desend amt of force dun push it further.

Have you tried tightening it more? (Just a small amount though) then try turning it left to loosen it??

failing that, a bit of heat may help you.

Tried both way. Didn't  moved at all. Mostly i tried anti clock wise

[Jules-C]

If it that tight leave it as it is and tie/hold caliper higher than master cylinder to bleed it.  Or use syringe to try pull air bubble out.

[rajoana]

went to a work shop. got all done.


even the mechanic had a tough time loosen those few screws....


and probably learnt something new. with his bleeding technique he pressed the pedal very lightly.


his theory was air bubbles come easier. if u were to press hard they might reach the end of nipple and go back in again. i guess must be true as i ever seen bubble going back in again. However i thought the solution was to press the pedal harder.[size=78%] [/size]