Q: Over heating problems

Based on what you are describing, typically a Mechanic would look for a faulty water pump, faulty radiator cap, plugged up, or externally obstructed, radiator, and/or non functioning electric cooling fans. However, your description of erratic operation of the temperature gauge introduces a complexity. Normally, when a car overheats, it just overheats; the gauge is buried on the high side and you hope the operator turns the engine off quickly so as to avoid warping of the head(s) or blocks. If you are seeing a fluctuating temperature reading though, it raises the possibility of trapped air and/or possible head gasket leaks. Of course, you could have a faulty gauge or sending unit, too. You want to first purge the system of air, if there is any. Test the radiator cap (the cap has to withstand a pre-set pressure). With no trapped air and a good cap, do a leak test. If the leak test is good, run the engine and see if you get continuous heat in the passenger compartment when temperature is set to hot with blower on high (if heat indicates water pump is circulating coolant). If pump is circulating coolant, use infrared thermometer on upper and lower radiator hoses and radiator. If, via these temperature measurements, you determine that hot coolant is not flowing throughout the radiator, you may have a plugged radiator (you still have to test and evaluate the water pump further, though). A plugged radiator will easily cause overheating. If no faults are found at any stage, you have to evaluate the possibility of a head gasket leak, specifically exhaust gases leaking into the coolant, which will cause overheating. An on-site exam from a professional would probably obviate the need for some of these steps and consequently I would simply suggest scheduling an overheating diagnostic by a certified Mechanic. You needn’t worry too much. On an issue like this, so long as the cause is not related to a leaking head gasket, there is a good chance this will be a fairly mundane repair once the cause is found. If you have further questions or concerns, by all means let us know.