[threedimensions]

So obviously I'm on here because I need some help...about a week ago my 06 325i started to overheat no other warning but straight to red overheating alarm. In response I changed the thermostat, flushed the coolant (which was very low) changed the oil and filter (as it was due anyhow). The oil should no signs of water so I ruled out the head gasket. So problem solved....so i thought! Today on a road trip pulling a fairly steep grade with A/C on the engine again alarmed a red overheating alarm. I pulled over as soon as i could popped the hood and seen coolant had came out of the expansion tank.

I am completely at a loss. The car does not overheat when the A/C is off and just the other night my wife pulled the same grade with no problem. Is it the water pump, expansion tank, sensor? By the way, the fan kicks on.

The car has been completely BMW maintained, maintenance plan warranty expired last October and i am the original owner. The car has about 90k miles.

I want to pull my hair out as i am completely at a loss please send me ideas. Thanks in advance.