M50i / N63B44TU3: Coolant loss / evap?

08-09-2025

chefwong wrote
I know we are discussing a V8 that drinks the green kool aid...

If coolant level lowers, there is a leak. Coolant doesn't just evaporate.

08-10-2025

For any of you guys experiencing mysterious coolant loss, I would absolutely 100% get an oil analysis done where they'll be able to check the oil for coolant contamination. That's a serious issue if there's coolant making it into the oil. If there isn't, it's much less serious but still a big question mark as to where exactly the coolant is escaping to.

08-10-2025

Prior to embarking on a 3300 mile road trip in June, I checked both coolant reservoirs -- both were at the MAX level indicator. Upon returning home, both levels were unchanged. The reservoir caps fit so tightly, I can't imagine coolant escaping through them, although maybe there are pressure release vents. Car ('22 X7 M50i) now has 7450 on its odometer.

08-18-2025

Maybe it's leaking somewhere that the dealer stated no leaks found.....A quick visual today, a month after the (topped off too high from the dealer), I can at least see the level indicator. Still high and more than the MAX mark, but it's able to be seen whereas post dealer visit, it was topped off to the point where I could not even see it.

Yesterday

I also had coolant loss and crust around the expansion cap tank. In 38,000 miles, I had never used the heater. I randomly remote started the car and the heater came on. I was told by a service advisor the coolant was funneled through the heat core and that's where the loss in coolant went.

Fast forward a week and I had a drivetrain malfunction and fuel injector 7 had seized. Turns out there was a coolant leak that dripped atop the fuel injector and caused it to lock up. Thankfully there was a TSB and BMW covered it under warranty. All fuel injectors were replaced on that bank.

Yesterday

N74B66TU2 wrote
I also had coolant loss and crust around the expansion cap tank. In 38,000 miles, I had never used the heater. I randomly remote started the car and the heater came on. I was told by a service advisor the coolant was funneled through the heat core and that's where the loss in coolant went.

Fast forward a week and I had a drivetrain malfunction and fuel injector 7 had seized. Turns out there was a coolant leak that dripped atop the fuel injector and caused it to lock up. Thankfully there was a TSB and BMW covered it under warranty. All fuel injectors were replaced on that bank.

Yep. Unfortunately a common failure for this and the S63. The crappy plastic expansion tank cracks/develops a leak which then leaks down into the injectors.

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M50i / N63B44TU3: Coolant loss / evap?