The ABS pump is passive when not needing to provide assist. The fluid just flows right through. I would highly recommend a Motive (or home made) Power Bleeder for this job. It makes it so much easier.

Using a power bleeder also prevents the master cylinder from getting over stroked which can harm the seals.

The one you have to be careful with is the SBS system on 2005 and 2006 W211s.

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The OM 642/722.9 powered family
Still going strong
2014 ML350 Bluetec (wife's DD)
2013 E350 Bluetec (my DD)

both my kids cars went to junkyard in 2023
2008 ML320 CDI (Older son’s DD) fatal transmission failure, water soaked/fried rear SAM, numerous other issues, just too far gone to save (165k miles)
2008 E320 Bluetec (Younger son's DD) injector failed open and diluted oil with diesel, spun main bearings (240k miles)

1998 E300DT sold to TimFreeh
1987 300TD sold to vstech