repeat the flush trying to get as much air out as possible and as much new fluid through the system as possible. Try bleeding the clutch system manually as well. Once done, if the problem still persists then there is some kind of mechanical problem causing this issue.

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2001 E55

2001 E320 Sedan

2001 Subaru Legacy

2006 SLK280

2016 Subaru Outback 3.6