Hello, I'm new here. I've got a 1996 Honda Civic LX with an automatic. About a month ago I discovered an overheating problem, but the weird thing is it only overheats when I move the climate control switch all the way to "cool". When it's about midway to all the way "warm" then it does not overheat at all. What in the world would cause that? The cap is pretty new, and I'm pretty sure there is no head gasket problem as there is no loss of coolant, no coolant in the oil, and no oil in the coolant. I am at a loss to what could possibly make the car overheat just setting the climate control to "cool". Please help!

 

Check whether the radiator fan fails to turn ON when the engine is hot.

 

Yeah, the fans come on, and the problem happens most while the car is on the freeway, or under load, so I don't think the fans have anything to do with the problem. I took a look today, and it appears that there is a valve that is opened and closed in a hose leading to the heater core when the climate control is moved from cold to warm. It also looks as though the thermostat is bypassed somewhat whenwater is moved through the heater core. So, I'm going to replace the thermostat to eliminate that. Thanks, I'll let you guys know what happens.

 

well i would replace the thermostat and if that doesnt help it i would replace the radiator.... it could be gunked up inside which could be preventing proper cooling....

 

The radiator was replaced about 12k miles ago and I looked in there and there was zero crud in any of the cores. I just replaced the thermostat though and that solved the problem. It appears that I was right about that valve before the heater core. When you put the climate control to warm, it opens that valve and coolant flows through the heater core and actually bypasses the thermostat. So if you're ever wondering why your car only overheats when the climate control is set to cold, replace your thermostat!

 

I had the same problem and it was the thermostat. It only overheated on the freeway while I was slowing down to an offramp.