The car is a 1998 Honda Accord with 250,000 miles.

The temp gauge goes into the red sort of randomly (mainly stop and start type driving). But it is not clear that the car is actually overheating. Turning on the air con/heater brings the gauge down (fans appear to work regardless of that). Car is idling low.

Took it to mechanic, they are suggesting a new radiator for $650, but aren't sure if that will fix the problem!

Thanks for any help.

 

Verify the primary cooling fan is working correctly, and verify there is no blockage of the radiator. Check in front of the condenser, between the rad and condenser and look for any fluid leaks/loss of coolant. Next verify the system is holding pressure and the rad cap is holding the correct pressure as well. Verify the coolant is properly filled and bled. If there was any recent work on the car prior to this overheating, recheck the work that was done it may be the cause of your overheating issues.

 

Did you ever find out what was causing your issue? I'm experiencing the same thing w/ my girlfriends 98 Accord Ex. Replaced the fan switch that seemed to work, but recently again only having the AC on will turn both fans on. I'm not interested in pumping anymore big money into this thing like Radiator, Water Pump, so I'm just trolling for something else I may have missed. Condenser and cooling relays are good.