I’ve got an M62, so take it with a grain of salt, but I think it’s the same radiator and aux heater pump setup on the N62 e53s. If so, I’ve read about lots of guys getting trapped air. I’ve always had the best luck draining via the large hose on the bottom right of the radiator…outlet I think, and it empties a lot faster. Then I fill as much as I can via the radiator inlet hose on the top left, next to the tank. Just dump it in the radiator with a funnel, and right into the pump, via the hose fitting, taking care to squeeze the hoses often, then continue filling. Then fill the tank as the last step.

The M62 aux heater pump bleed method has always been a 100% solution for me.

I’ve got to replace the coolant tank sensor, on the bottom of the tank and would rather not drain the coolant too much. I’m wondering if I can get enough out of the tank with a pump or turkey baster, etc. so I don’t make a huge mess.

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Current
Original owner 2002 E53 X5 4.4i to 4.6i swap
2026 G80 M3 6 spd
2025 G06 X5 50e
Former
1972 Audi Fox
1986 Saab 900S
1996 BMW Z3
1998 BMW E36 M3 Sedan
2004 BMW E46 M3
2006 Audi A3 Quatro
1993 Mopar 318 Jeep Grand Cherokee
2015 V6 Jeep Grand Cherokee