Check the coolant level after the engine has warmed up for ten minutes,Check the engine coolant and see if it is circulating through the radiator properly,If the engine coolant is brown or dirty and seems to be weak, the entire cooling system may need to be flushed, that is, cleaned out with a radiator and engine cleaner, PRESTONE radiator cleaner works well in this type of problem.IF that does not fix the problem , you may have to overhaul the cooling system,...(I.E)... replace the thermostat, have the radiator cleaned at a radiator shop, replace the water pump,replace the upper and lower radiator hoses, and flush the engine cooling system with Prestone engine block, coolant flush...Check the fan belt tension and make sure the cooling fan is working properly as well....