I have a 1996 Honda Civic, it only overheats after driving for about 45 minutes, then it goes from normal to in the red immediately, If I turn the heater on it return to normal. There is no smoke coming from the exhaust, the oil looks normal, I did notice a little soapy stuff in the radiator when I opened it for a short time and ran the engine and it warmed up. When the heater is turned on the temp returns INSTANTLY to normal, and when I turn it off it INSTANTLY heats up... Thanks for the help

SOURCE: 95 honda civic lx overheating

COULD BE COOLANT SENSOR,HEAD GASKET,CHECK THE TIMING,THE PROPER MIXTURE OF COOLANT,WATER PUMP.DID YOU HAVE IT CHECKED OUT?ANY LEAKS?HEAT WORK WITH FAN?

SOURCE: car overheat

The rad fan is required to keep your engine at a normal operating temp. When you are going at hiway speeds the fan is not needed. When you stop then the fan has to operate to keep the engine cool.If the fan is not operating, it could be the fuse or fan relay or temp sensor or computer This problem should be checked by someone who is a professional..

SOURCE: What could make my 03 civic ex overheat and cool

your heater has apparently restricted the coolant flow....hopefully a good system back flushing will cure the problem....use a flush obtained from a parts house....I would buy the hose kit for flushing as well...good luck to you

Testimonial: "thank you"

SOURCE: changed radiator on94 honda civic now car

verify the plug of the fan and the fan switch located in termostat housing, if all are pluged in remove the conector of fan switch and short it with little piece of cable, if fan turn on replace the switch! it cost around $20. if the fan no turn on when short the conector verify if the fan conector have 12v if have it changer the fan motor if not check the fuse.