Front brake line replacement

I need to replace the front o\s brake line for the mot. When I unscrew the old one from the ABS unit will fluid drain from the ABS.Is it straight forward to bleed from the caliper as usual ?

As i remember, on diagnostic tool there are special function INPA/DISA, after for example fluid replacement to circulate the brake fluid by ABS unit. But from practice, yes, you can bleed from caliper, some notes, don't open fluid reservoir before you finish change the lines, need for ABS unit not to "swallow" air in. And just after you can open reservoir, fill it /refill it, and open calipers, from the longest line side, as usual.

I think if you keep pressure on the brake pedal while doing the works there is a non return valve that should prevent air ingress

There's not much reason for fluid to drain out of the ABS pump and let air in if only one pipe is off so straight forward bleeding should be ok. As said, INPA does have a full ABS pump bleed function but it's a bit of a two person job and a bit arcane. Had to fully remove the pump from an E90 to change the vacuum servo once and so ran through it and it must have taken us about 3 attempts to get the sequence right (it shouts instructions, wants keypresses to reassure it and to have bleed nipples opened and closed at just the right moment!)

peterh said:

I need to replace the front o\s brake line for the mot. When I unscrew the old one from the ABS unit will fluid drain from the ABS.Is it straight forward to bleed from the caliper as usual ?

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I've done this on a couple of occasions. I just remove the old and insert the new VERY quickly. Fluid loss is negligible. Then bled the system immediately with my pressure bleeder which makes the process very easy. No issues and no problems afterwards