If you search for bmw on that board you get some scary threads.
I love the one about bleeding an m20 and they realize it is a stuck thermostat.
I am not a tech, but generally when I do a pump I replace the thermostat and bleed the system.
I dated a young lady who had a LeCar ( remember that POS ?) that had to be pressurized to cool. It had a pump handle on the overflow tank that had to be pushed 18 ( not 19 , per the manual ) to effectively cool.
89 525, 86 jetta diesel, 07 wrx with mods, 06 commander
1 mean wife, 2 daughters, 1 bull mastiff. At least the jetta
is cheap to keep up.