On my girl's civic after she drives around for a while, 15+ mins of city driving, and we get out of the car the coolant in the reservoir is boiling. The cars temp gauge appears to be working and is never showing that the car is hot.

Any ideas? Radiator, radiator cap, air in the coolant system, not enough antifreeze per unit of water?

 

half anti-freeze half water

 

I know that there is susposed to be a fifty fifty mix of water and antifreeze in the radiator and I am sure that it is not quit that high, I know there is some antifreeze with the water but, would that cause the mixture to boil in the reservoir??? I thought you could run straight water with no problems as long as it doesnt freeze??

 

could be the temp gauge is broken, and you have

A. bad thermostat
B. the fan is not working

Is the fan working (visual confirmation because you have 2)?

 

I am pretty sure that the guage is not broken, it reads a little under half way which is where they normally run. I do not know if the fan is working or not I will check it tonight and see if I can get it to come on manually and then see if it comes on by itself when it is supposed to.

 

well, it's not a good idea to run straight water for a couple reasons. Number one, is because anti-freeze provides an anti-corrosive element to the coolant. If you run just water, it will corrode your insides. Number two, The anti-freeze provides a lubricant for the water pump. You should run down to about 10% anti-freeze in the mixture, but not much lower than that.

Redline Water Wetter provides the above things when mixed with water, plus increasing the efficiency of waters cool

Water does a much better job at cooling than anti-freeze does, so you are right to want more water in there (Don't use 50/50 unless it's freezing cold winter).

You should also be using Distilled water, not tap water...are you?

When was the last time your coolant was flushed?

And check the thermostat and rad cap.