That is a double flare not iso flare tool. I couldn't locate an inline iso flare tool like the one you used. I suspect you tried a non iso version of the bar tool as well. Double flare might work with iso fitting but it's not the correct fitting and can fail under pressure. Flare fittings get weaker under pressure iso fittings tighten under pressure.

A "bubble flare" is open to the fluid pressure at the junction and the fluid pressure pushes the joint into the seat vs double flare where the pressure pushes the joint away from the seat.

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2011 E70 • N55 (me)
2012 E70 • N63 (wife)