Q: 2008 chevy Malibu 3.6 v6 over heating after water pump replacement

Overheating will warp the cylinder head and/or engine block causing costly damage so be sure to get this resolved right away. Indeed, it is best not to drive the car if you know the engine is operating outside the normal temperature range. The most common causes of overheating include low coolant level, a faulty thermostat, a plugged radiator, a faulty radiator pressure cap, collapsed hoses, non functioning cooling fans, and a faulty water pump or drive belt. In your particular circumstance, I would look first at the engine cooling fans as you are indicating that the overheating is occurring at idle (presumably when you are stopped) when those cooling fans are most critical for radiator cooling. At speed, there is airflow and thus the fans are less critical. Certain engine faults, such as a leaking head gasket or poor engine running condition can also cause overheating. If you desire that this problem be diagnosed by a certified Mechanic, dispatched by YourMechanic right to your location, please request an engine overheating diagnostic and the responding certified mechanic will get this resolved for you. If you have further questions or concerns, do not hesitate to re-contact YourMechanic as we are always here to help you.