Q: Truck is overheating and heater won't work

Hello. The symptoms you describe are commonly associated with air bubbles in the cooling system. If the cooling system was recently serviced then it may be possible that it needs to be properly bled of air bubbles. Air trapped in the cooling system can cause hot spots, which can lead to engine overheating as well as heater malfunctions, if they prevent coolant from getting to the heater. Another thing to look at would be the vehicle’s heater control valve, the component that controls coolant flow to the heater. If the valve gets stuck, or otherwise malfunctions, it may prevent coolant from reaching the heater core, which will lead to no heat. Another possibility is a worn or faulty water pump. A water pump with a worn impeller may no longer be able to properly circulate coolant throughout the engine, which can cause both of your symptoms. As cooling system issues like these can sometimes be difficult to diagnose, I would recommend having a professional technician, such as one from yourMechanic, come to your location to diagnose what may be causing your issues.