Wifes car is sporadically overheating when driving in slow traffic. Only seams to do it when she drives it. Changed thermostat last year when she had the same problem and the issue went away. Well a year later its doing the same thing. Find it hard to believe another thermostat is sticking from time to time but I guess stranger things could happen. Not thinking water pump because it doesn't appear to be any leaks at the pump. Seams a water pump would either work or not unless the housing is worn and its not moving much coolant. About to put another thermostat in but wanted to see if anyone here had any thoughts first. 107,000 miles on it.