Anybody have an idea why my Ls1 would show to be over heating according to car temperature gauge at idle on passenger head sending unit. Have a new sending unit and gauge shows to be good. The drivers head which has computer sending unit shows to be normal range. New thermostat, new water pump, radiator has been flushed, heads re-done. Put squirrel cage fan in front of radiator, doesn't bring temp. down. Tells me it's not a air flow problem, but can increase rpm 2 or 3 hundred or start driving and temp comes down to normal range on car temp gauge. Would i be correct thinking i must have air in the system?