Kim Suchodolski

Hi I have had my 99 Civic for 12 years now it has been getting hot and overheating on warm and cold days if I let it idle too long like at a stoplight or drive thru... We have replaced thermostat twice, radiator, hoses, etc... it is not leaking water.. if I turn the AC off it cools down some but I sometimes have to turn on the heater to lower the temperature arm ... thinking maybe water pump?? it has 198k on it original motor, tranny, clutch etc been a great car any suggestions

cbaber

Radiator fan. When you turn on the heater you are essentially putting the coolant through another radiator that transfers the heat into air for the cabin. If it only overheats while stopped that means the radiator fan is not moving air through the radiator to cool it.

Let the car idle in your driveway until it gets to normal range. Watch the fan. Does the fan ever turn on before/after it starts to overheat?

Could also be the water pump. At idle the worn down blades might not be able to circulate enough coolant to keep it cool, but at higher rpms it does just enough to keep it running cool. Usually you can tell if you have it in your driveway or on the road because if it starts to overheat just rev it up for a bit and the temp should drop.