Coolant Loss Issue - BMW F36 430i B48 (LCI 2018)
Hi everyone,
I wanted to share an issue I’m experiencing with my 2018 BMW 430i (LCI) with the B48 engine. The car currently has 115,000 km (approx. 71,500 miles), and I’ve noticed a mysterious white residue appearing in the engine bay.
The Problem:
Dual Coolant Loss: I am losing coolant from both the main (high-temperature) and the secondary (low-temperature) expansion tanks.
Location: The white, crusty residue is concentrated in the front area between the engine and the radiators/cooling fan.
Contamination: There are fine white spray dots on the rubber hoses and electrical components, suggesting the coolant is being sprayed under pressure while driving.
It seems to be a common weak point for the "3er" series (3 and 4 series models), often related to brittle plastic vent pipes or connectors that fail around this mileage. Since it is affecting both independent cooling circuits, I suspect either multiple failing plastic lines or an issue near the radiator stack where both systems are in close proximity.
Has anyone else dealt with leaks from both tanks simultaneously? Any specific hoses or connectors I should check first before I start tearing things down?
Thanks for the help!