How to fix coolant 528i 2012 n20

Hi, this is Bo, an auto expert on RepairPal's Car Genius team! The coolant under the reservoir of your 2012 BMW 528i suggests a leak, likely from the reservoir itself or the hoses connected to it. The N20 engine is notorious for cooling system issues as it ages. First, check for cracks in the reservoir or loose hose clamps. You might even have a failing pressure cap, which can lead to overflow when the engine heats up. If you spot a crack or leaking connection, replacing the reservoir or tightening the hoses should do the trick. Just make sure to use BMW-approved coolant when you refill it. If you need any further advice or want help finding a trusted RepairPal shop in your area, please feel free to call us at 877-913-1554!