Rep Power: 0

I have a 2003 Honda Civic LX that has been having a few overheating issues and symptoms. The radiator cap and thermostat were recently replaced (since it was cheap/easy replacement) and seemed to slightly help the overheating at idle frequency. The radiator fans were checked and seem to be functioning properly, no visual leaks of coolant and hoses appear to be in good condition from the outside. The car never overheats if the cold A/C is on while driving, only if the heat is turned on. The HG was a thought, but would like to rule out easier/cheaper possibilities - the car has almost 200,000mi if that helps. Any ideas?

• The overflow reservoir will fill up completely (but does not overflow out the cap - it stays about 2 inches below cap) and not drain back into the radiator even after if has cooled down (leaving radiator looking empty).
  
• The car will occasionally overheat while idling (extremely sporadic).
  
• It will also overheat when you turn the cabin heat on almost immediately (but will usually push hot air). This is a newer symptom in the last 2 months.
  

 
Rep Power: 368

headgasket.

https://www.civicforums.com/forums/3...reference.html

test yourself