Ok, you expert DIY'ers, here's a lil' quiz for ya. Look at the picture; now what do you think caused this? The expansion tank is brand new.

Choose the correct answer below. Only one answer is correct:

A) The engine overheated expanding the coolant beyond what the cooling system could handle;

B) The expansion tank has a manufacturers defect;

C) The coolant was overfilled causing over-pressurization of the cooling system;

D) The coolant got extremely hot thus melting the expansion tank joints.

Attached Images

 

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'05 E53 X5 4.4i, '97 E39 528, '07 E92 335i, '16 F86 X6M.