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Brakes won't bleed

I

ibdave

Bicycle
Left side front brake failed at the spring fling. Put a bolt in and rode home on one disc - nice firm feel. I have replaced the piston seals and dust seals on both front calipers. Cleaned them up and removed dirt and corrosion in the seal groves and installed new pads to both sides. I bled the right side with a mity vac and it seemed to bleed as expected. Tried many times to bleed the left side, one bottle of DOT 4 later still sucking many large air bubbles. The lever is spongy and comes very close the bar. It will firm up some if I pump the lever a few times. Any suggestions? Is it possible the air is sucked in by the new seals? There is no brake fluid leak.
 
I replied in a way on the listserv but if you have not used a vacuum to pull down that should work. I know it worked for a guy just a few weeks ago. ---------------------------------- I will answer any question. It is up to you to figure out if I should have.
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I just installed 4-piston calipers. To get them bleed, I opened one bleed screw at a time and let the fluid run for a few minutes to fill up the calipers. Leave the lever out and keep the reservior filled. They would not bleed properly until I did that and then pumped the pistons and pads hard against the discs. Try that on your rebuilt caliper. After the calipers were full and tight, I only pumped the lever 8 or 10 strokes. John '05 Concours w/170/60VR-17 '00 748/853 "Rosetta" Chattanooga COG #7914 IBA #33000
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Suggestion from Boomer that air might be leaking through the bleeder threads seems correct. I used plumbers teflon tape, and this helped when using my 'Mity Vac' pump. However it is the pump that sucks the air through the threads. Did the final bleed the normal way by pulling the lever (helps to have a helper) while loosen the bleed - no bubbles.
 
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