A common cause of over heating the Pontiac V6 engine is a air bubble in the cooling system. Bleed out the air and make. My temperature gauge stays normal, the rad and overflow are at correct levels,but my block is overheating. I had a temp. gauge on my catalytic converter and. having lots of overheating problem with Pontiac Sunfire () changed thermostat, replaced water pump, now am flushing the radiator, I also noticed when the.