Q: Car overheats and coolant reservoir makes a hissing noise

Malfunctioning fans will typically only cause the car to overheat at idle or in traffic. Of course, if the fan is not functioning it should be replaced and that can be accomplished by a mobile mechanic if you request radiator cooling fan service. If the vehicle is overheating on the open road, there is likely a problem in addition to the fan. The most common causes of overheating include 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, and a faulty water pump or drive belt. Certain engine faults, such as a leaking head gasket, poor engine running condition or exhaust blockages can also cause overheating. If you desire that the overheating 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.