I have a recently purchused 1990 honda civic dx special edition four door. It has 290 thousand kilometers on it. It has a overheating problem, it is perfectly fine just sitting and idleing for a half hour fine but as soon as i take it out the temp gage sky rockets to full heat with in about 4 minutes. when i park it steam appears to be coming from the rad cap. I have already reaplaced the thermostat and am wondering what the problem could be. aas of yet i have not seen the fans working, but would the fans not running be enough to make it over heat that fast. I am going to do a pressure test on it and if it is low below 13 am then wondering where to go from there. i squeezed the upper rad hoast and there appeared to be pressure in it, so i am fairly confident the waterpump is working. what is the most common cause under these curcumstances.

 

try bleeding the system. Simply take the radiator cap off when the engine is cold. Then turn the car on and turn the head up to full blast. Add fluids if needed.

 

also feel the radiator hoses, if the top is hot and theb ottom is cold it could mean bad thermostat, even though you replaced it there have been cases of them being bad out of the box, just a thought. You can rule radiator fan out becasue you DONT overheat at idle (stopped i'm assuming?), but bleeding the system is definitely your first step.

 

The 1991 and below radiator fans are controlled by engine temperature, so the fan should absolutely come on when the engine starts to overheat.

This is controlled by a switch on the back of the engine block near the oil filter (the switch with two wires, the one with one wire is for the oil pressure light). Disconnect the switch and jumper between the two wires, the fan(s) should now come on whenever the key is on. You can test drive like that to see if that solves the overheating.

If the car has air conditioning it will have two fans, both fans should run and stop together.