My 1993 civic lx temperature gauge needle approaches the red line in 5 mins after starting. I replaced the thermostat, but the same hot temperature occurs. The cooling fan did not come on, but it works as a direct power line from the battery to the fan turns on the fan. Can the high temperature be caused by the cooling fan relay swithc not working or is the water pump inop or? Will flushing the radiator fix it? There is no leaks with the radiator.
Yes, the high temperature can be caused by the cooling fans not working. If you are lucky you haven't caused the head gasket to blow yet, but it could be bad.
As far as the fans not coming on it is most likely the coolant temperature switch or the cooling fan relay. Once you get that fixed you can see if the overheating problem goes away.