brake rebuild problems

[Foolber]

so iv got this 1978 xs1100 in here that im doing a complete rebuild of all brakes on and im having trouble getting the front to build any pressure. to get you up to speed both calipers cleaned and rebuilt, MC cleaned and rebuilt, all three rubber lines replaced with new rubber. new washers and banjo's.

so iv got fluid running all the way threw the system but cant get any real pressure in the lever, there is enough to bleed the system but not enough to move the pistons in the calipers, i have air bubbles popping up every once and a while in the master cylinder, mostly small ones but occasionally will have a couple bigger ones. any ideas?

[Courtney]

Do you have a mighty-vac brake bleeder or harbor freight clone? Also, put teflon tape on the bleeder screws so that it is airtight when bleeding so no air can get past the threads. Use a might-vac to push brake fluid up to the master cylinder so that the air bubbles get pushed up and out of the calipers and lines. That's what I'm about to do on my total front brake rebuild. I'm sure others will chime in with another way to do it too.

[BigOates]

Try wrapping some Teflon tape around the bleeder screws to make them airtight. I did that and used a vacuum bleeder yesterday and had them good to go in about 15 minutes. Just make sure not to let the master cylinder suck in air since the vacuum bleeder can pull a good bit of fluid pretty quick. I got mine at HF yesterday. On sale this month for 25 bucks. If not you could probably borrow one from one of the local advance auto parts or autozones.

[jetmechmarty]

It's likely that all you lack is patience. It's a chore getting these things bled. You're using DOT 3, correct? Fill the reservoir, tie the lever back, and go do something else. It can be a chore, even with a Mityvac.

[Foolber]

It's likely that all you lack is patience.

LOL. No. i sat there for 3 hours pumpin that puppy last night, and i dont have a vacuum bleeder, (did think about goin to the advance though to get a loner if possible) i usually use the lever just fine. i fill my calipers first also, but not my lines.

when you talk about tape on the threads you mean like plumbers thread tape? wont that just get ate up by the brake fluid and go into my calipers and lines

[DGXSER]

Have you "bench bled" the master? Often I find if I pull the line off the master, put my thumb over the hole where the line goes, pump will it pushes my thumb off, repeat, then put the hose back on quickly not to let air back in. I get a much stronger lever from there on out.

[Foolber]

Have you "bench bled" the master? Often I find if I pull the line off the master, put my thumb over the hole where the line goes, pump will it pushes my thumb off, repeat, then put the hose back on quickly not to let air back in. I get a much stronger lever from there on out.

no iv never had to do that before either, didnt want to take off the masters yet, trying to knock all other options out first. rear brake is doing the same thing, im thinking about gravity bleeding them overnight. iv never done that, do you just pop the bleeder and ziptie the lever down?

[Foolber]

I picked this puppy up for 7 bucks lol. Ill give it a try. How do you edit posts?

http://m.advanceautoparts.com/mt/sho...n_jtt_redirect

[donebysunday]

I picked this puppy up for 7 bucks lol. Ill give it a try. How do you edit posts?

http://m.advanceautoparts.com/mt/sho...n_jtt_redirect

Interesting, may use in the future ?
When I had trouble with the front left add on disc and caliper on my XS650 I used a 2 stroke syringe made for mixing oil/fuel mixture to suck the fluid into the caliper with a bit of fuel line on the nipple. Check the MC for fluid often.

[motoman]

Any luck yet? If not, remove master cyl. cover, tie lever back up against a block so lever only goes half-way back. Leave overnite to alow any air bubbles to rise and escape master.

[Foolber]

Any luck yet? If not, remove master cyl. cover, tie lever back up against a block so lever only goes half-way back. Leave overnite to alow any air bubbles to rise and escape master.

yea no luck, that bleeder thing is worthless lol. i think ima try the gravity thing, i cant get any pressure to build up in the rear cylinder, the master i have filled at least 5 times, so i know iv go fluid all the way threw but might have air getting in somewhere. not sure were that would be though....no fluid leaks yet so far.

[Foolber]

Any luck yet? If not, remove master cyl. cover, tie lever back up against a block so lever only goes half-way back. Leave overnite to alow any air bubbles to rise and escape master.

yea no luck, that bleeder thing is worthless lol. i think ima try the gravity thing, i cant get any pressure to build up in the rear cylinder, the front master i have filled at least 5 times, so i know iv go fluid all the way threw but might have air getting in somewhere. not sure were that would be though....no fluid leaks yet so far.


oops double posted that one.

[CaptonZap]

When you tie the lever back, look at the brake lines, and make sure that there is no horizontal portion of the lines. You want them all up and down. You may have to put it on the side stand and cock the wheel one way or the other. Pay attention to where the lines goes into the splitter, (if you have stock setup), and make sure that if there is a bubble inside, anywhere in the system, that it is uphill to the MC. It will float up there overnight.
CZ

[bikerphil]

I am surprised that no one has mentioned the possibility of the MC plunger seal reversing itself due to the lever being pulled in too far during bleeding.

[DGXSER]

To bench bleed you do not need to remove the MC. Just wrap the area in a towel, break the banjo loose at the Master and remove it keeping the brake line up high. Now put your thumb over the hole the banjo bolts to. Squeeze the lever holding your thumb tight over it. If the pressure does not push your thumb off, hold the lever squeezed in, and quickly pop your thumb off and back on to let any air out. Now release lever and repeat until it pushes your thumb off. It will squirt fluid past your thumb when its bled.

Now have the banjo bolt and washers in place with the line right by the master. Now let your thumb off and quickly put the bolt in.

This will also help with the rear system but harder to do.

Phil, I was thinking if the "bench bleed" fails, that would indicate that type of issue.