replace overflow tank cover

Came to Chev Center in because rattle under car and hissing. Classic Symptoms of bad catalytic converter. Causes over heating and poor fuel mileage. Worker did not check to see if catalytic converter was bad. Worker just brushed me off. Worker just treated a result of bad cat converter not the cause. When I asked about the rattle, worker just said caused by string hanging from door. Ha Ha. Coordinators who take info on cars are inexperienced and untrained. This lack of skill by those working on cars has cost me $800 in extra repairs so far and Cat Converter is not repaired.