Q: I have a 2010 GMC Terrain that is overheating. I found out it only had about a quart of coolant.. what is my next step?

If the car is still overheating, even after filling the coolant system (and making sure there is no trapped air, which itself will cause overheating) just request an overheating diagnostic during which a certified mechanic will determine which of the most common causes of overheating are relevant in your case - namely low coolant level (including that due to leaks), a faulty thermostat, a plugged radiator, a faulty radiator pressure cap, collapsed hoses, non functioning cooling fans, a faulty water pump or drive belt, or engine faults, such as a leaking head gasket or poor engine running condition.

If the car is not presently overheating, and you have refilled the cooling system, the next step would be to monitor the coolant level in case there is a leak. If the coolant level in the reserve tank falls over the course of days to weeks, you have a leak and to resolve that just request a coolant leak diagnostic. Engine coolant can leak externally through a hose, radiator, water pump, etc. or internally due to a leaking head gasket and sometimes a leaking intake manifold gasket depending on the engine design. External leaks are typically found by simple pressure testing of the cooling system. If you have further questions or concerns, do not hesitate to re-contact YourMechanic as we are always here to help you.