James, I did not read the rest of the thread, but I would find a helper that is attentive and reliable and bleed the brakes with the two man method while engine is running.

This has solved the issue you describe many times for me, when doing lots of work on the brake system and having bleeding problems.

Best of luck with it.

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2001 SLK 320 six speed manual
2014 Porsche Cayenne six speed manual

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