how?

[bronze mirage]

I went to school and there was nothing wrong with my coolant. After class I started my car and boom. Coolant is low. Once I started to drive a lil it alerted me that the car was overheating. I went to go buy coolant and after driving for a few mins there was no more coolant. I checked under the car and it was leaking. Brought it to the shop and they found 2 leaks. How did this happen? My bmw was perfectly fine driving to school

[dense wharf]

Is this an E46? Common failure point is the expansion tank. Fine when cold, then it heats up and leaks, but the radiator still has coolant so the driver doesn’t notice. Then you park it and ordinarily as it cools off the coolant moves from the expansion tank back into the radiator as it shrinks. But the expansion tank is empty because leak, so it cools and sucks air in instead. Then boom, low coolant next time you start it.

[edgy pewter]

Plastic and rubber parts don’t break slowly under pressure. If it was workhardend enough to the point it becomes brittle in one spot; one more cycle and it will break

And bmws love to put plastic on engine components; where it shouldn’t be plastic

Very shit quality plastic too sometimes

IMO I think it was either a rubber hose failure or an overflow failure