Coolant flush on N55 - DIY guide

Good guide. One important thing to add - the N55 has a bleed screw on top of the thermostat housing. After filling, open this screw and let coolant flow out until theres no air bubbles. Then close it and run the engine with the heater on full blast for 10 minutes. Check the level again after it cools down. Air pockets in the N55 cooling system can cause overheating.

Always use BMW-approved coolant (blue) or Zerex G-48. Never mix green and blue coolant - they use different corrosion inhibitors and mixing them creates a gel that clogs the system. I see this mistake at the shop at least once a month.