You can crack oopen the two fittings on the lines coming down from the MC and let fluid flow some (don't let the fluid resevoir empty). this should allow any trapped air to rise back to the MC and, probably, into the bottle.

Worth a try.

Also, three bleedings is not unheard of when so much of the system has been replaced, especially when calipers are replaced.

Don't lose heart!

While opening each bleeder screw, tap on the caliper with a small hammer. This helps loosen air bubble still clinging to the insides of the new caliper.

the better way to bleed is to use a pressure bleeder, like EZ Bleed. Tromping on the brake pedal can force the MC piston in a manner which fails its seals, causing pool pressure.

Check the FAQ
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1989 740Ti 1986 240DL 1984 244GL