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Discussion Starter #1
I observed something odd while bleeding my brakes today. While bleeding the front passenger side, after a few seconds I got an unusually large amount of air bubbles. I watched it for 30 seconds, then decided to tighten the bleed nipple.

I was trying to figure out how what I saw was happening - bleed nipple closed, but pockets of air were still clearly seeping out of the little hole in the bleed nipple. Can anyone give me a clue as to whats going on?

I'm using a motive bleeder, wet method, but my understanding is that shouldn't matter. With the bleed screw closed the system should be shut off, i.e. not makin bubbles.
 

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the bleed hole is actually above a cone shaped solid metal end of the bleed valve.

So the cone is closing the port to the brake fluid, but the vacuum bleed system can still pull air through the hole through the bleed nipple valve. The air is just going by the threads. If you had thread sealant on the threads, then there wouldn't be a path for the air. But it doesn't matter.

That is the reason why I always finish with a manual push bleed, with no vacuum. Easier to see when you have a final bleed and no air in the system.

 

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Discussion Starter #4 (Edited)
I should add that eventually it stopped, and that I reopened the bleeder and got more/the rest of the air out and then closed it, but I'm still miffed as to whats going on here. Even though I'm not using a vacuum the description and pictures help me understand how what I'm seeing could be caused.
 
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