impossible bubbles while bleeding rear brakes

[greg78gs750]

hi guys,

78gs750. i just bought and made up new ss brake lines from earls. easy enough. i also, after examining brake threads, invested in a mity-vac. my question/problem is this:

when i have tried to bleed the rear brake, i get an IMPOSSIBLE number of bubbles from the "inside" bleed nipple. i have run almost a whole bottle of brake fluid thorough the system, and it is still bubbling like mad. like, as in, how could this much air be in the system at all??? i am not seeing any leaks anywhere, not from the lines or the caliper or anything. so.....where are these bubbles coming from?

also, i "think" i could use new rear pads.....anyone have a pic of what they should look like? my clymer manual shows a "shoulder" on the pad, but on the fische the pad looks shoulderless.....though, admittedly, those online fische do suck.....

any help would be great, i wanna get back to riding!!! (which is why i did the back first, i figure if i screw it up i can go without a back brake.....i know, i know, im just sayin......

thanks guys!!!

greg

[AOD]

Try bleeding without creating a vacuum with the mighty vac. Pump pump pump, open valve, pump slow, tighten valve. Repeat.

Does this bubble still?

I found the mighty vacuum can suck air past the nipple on the brake caliper, which makes it look like it's coming from inside the caliper...

~Adam

[greg78gs750]

i wondered if this could be it... i will go try it. thanks!

[bwringer]

Try bleeding without creating a vacuum with the mighty vac. Pump pump pump, open valve, pump slow, tighten valve. Repeat.

Does this bubble still?

I found the mighty vacuum can suck air past the nipple on the brake caliper, which makes it look like it's coming from inside the caliper...

~Adam

Right -- the air is coming from the threads on the bleeder, not from inside the system.

You can wrap the threads on the bleeder screw with teflon tape, as used in piping, to help seal them.

[greg78gs750]

ok. well, i haven't actually tried it yet, though i am sure this is the problem. now, however, my wheel is experiencing severe drag.....is a caliper rebuild in my future? how, exactly, do these calipers work? do they just "spring back" on their own, or are they "sucked back" by the m/c? if they aren't springing or sucking, should i take them apart? what am i saying....of COURSE i should take them apart.....hehehe.....well, here i go.....

[dtkid]

If you put 'brand new' pads on the calipers you'll often find that they will indeed heat up the disk.......for a bit. Make sure you manually pull/push the caliper piston all-the way back before install the new pads.

I've found that no matter what I do..........(and correctly) the pads will initially drag the disk for a couple of miles until they "seat" with the disk. I think a person should be very careful during the first 30-60 miles after installing new rear pads on these machines.

That is of course, my opinion, but if we decide to keep these old (antiques) machines on the road we need to learn to a bit of patience and care.

[greg78gs750]

welllll...........it is a miracle my rear brake worked at all. really. SO MUCH CRUD in the caliper. so a rebuild kit will be ordered tonight. the master cyl is gonna have to wait till this winter. as long as i am ordering, i should probly get the front too, eh? ugh. i wanted to ride this weekend. maybe this is the excuse i needed to get that shiny new sv.......honey? can i getta nother bike???? pretty please?????

[dtkid]

clean it good.......you might be surprised how well they clean up and how durable they actually are. Remember, these machines are truly over-engineered....stuff works, most of the time, after decades of neglete. (These ain't Harleys!!)

Before you ever buy kits.....give em' a good cleanin'.

[Pearson]

brakes

Hey greg78gs750 you may want to check my thread to see if there are any similarities:

http://www.thegsresources.com/_forum/showthread.php?t=105824

Also, don't forget to adjust your break pedal adj. screw when you add new pads. As for me, I overhauled my calipers on my dining room table with lots of mild degreaser, lint free towels and cans of air. Take your time, keep everything sterile, use a scrunge lightly and only scrub in the direction of the piston, not perpendincular if that makes any sense. Same goes inside the piston seat.

Let me know if you need any help.

[almarconi]

Chances are if your rear caliper was loaded with goo then the MC is probably dirty also, mine was. The hardest part I found was getting the caliper pistons out of the bores..mine were pretty rusty. The pistons cleaned up so all that was needed were some fresh seals. Remember when you reassemble the seals and piston to you clean brake fluid on then so they don't tear. I own four cars and 2 bikes so I am well versed in servicing brake systems. I gave up on trying to pump the MC to remove air when bleeding the brakes..the best money I spent was on a phoenix injector to bleed brakes. I use this tool to inject fluid up through the caliper into the MC. The trapped air rises up through the fluid and exits the MC. Bleeding brakes becomes a one man operation. You can also perform pressure and vaccuum bleeding. I have also used the tool to flush/clean a/c system components.

[psyguy]

also, i "think" i could use new rear pads.....anyone have a pic of what they should look like?

new pads have a groove in the middle
you can use them till that grove disapears (thats the limit of wear you should have on the pads)

[greg78gs750]

well, yeah. took apart both calipers, both are oocky. so, hi ho, hi ho, to the parts guys i go.....thanks for all the responses!!!!

btw, i "think" i can just get new seals/rubber and call it good, the pistons etc are actually in good shape....thinking about stripping and polishing these suckers as long as they are off.....

greg