Do you mean the temperature gauge is going beyond half way? Coolant disappearing is not normal. If no external leak visible, a combustion gas test needs to be performed to rule out a bad head gasket. Catalytic converter will not cause the coolant level to lower or engine to overheat. June

Coolant disappearing is not normal. (+1) If no external leak visible, a combustion gas test needs to be performed to rule out a bad head gasket. The coolant is probably smothering the engine combustion. The liquid is around $8 to $10 dollars. You can borrow/loan the bulb kit from O'Reilly or Advanc...