Bleeding master cylinder necessary?

[rallysam]

I managed to empty my brake fluid resevoir and pump air into the master cylinder. On these Legacies, do I have to bleed the master cylinder now? Or will the air work it's way out if I keep bleeding the four calipers over the next couple weeks?

[Legacy777]

I would probably go ahead and bleed the MC.

What I would do is crack the lines on the MC a little, and try and work some air out. If it looks good....continue with rest of the system.

Drive for a week or two....Then re-bleed the brakes.

[vrg3]

Legacy777: What's the procedure for bleeding the master cylinder? I looked before for a bleeder screw under there and didn't see one.

rallysam: I think I let air get in through the master cylinder once when I didn't top it off properly while bleeding, and I ended up doing one complete round of bleeding the calipers, and then another complete round. I probably ended up flushing pretty much all the old fluid out, but it apparently worked.

[whitemr2]

I'm not sure if the Legacy is any different, but the procedure for some other cars is this (requires two people):

1. Detach the brake lines from the MC.
2. One person slowly pushes brake pedal down all the way and holds.
3. Other person plugs the two brake line holes (on the MC) with fingers.
4. Person #1 slowly releases brake pedal.
5. Person #2 removes fingers from brake line holes.
6. Repeat a few times.
7. Reattach brake lines, and bleed all brakes.

Naturally, this will make a mess and lots of paper towels will be needed to ensure no fluid gets on any car parts (remember, it'll eat through your paint!!!).

Your local autoparts store might sell a one-man bleeder system with an adaptor to hook up to the MC.

[Legacy777]

look for one of those kits that will basically hook up to the MC, and feed the fluid back into the MC.

That's the best solution. Then try not to let air get back into the MC when connecting the lines.