Just recently I've been having this issue at least once or more a week where my car will go to the halfway point or more on my coolant gauge and won't like to come down. If it does then it shoots back up not too long after. My car is a 95 civic dx coupe with the 1.5l. At first I thought maybe it was the cooling fan not kicking on, but it does. I also thought maybe it was the thermostat but the upper radiator hose gets warm and if that's warm then the thermostat is working. I checked the fluid but the weird thing I found is that there was a lot of coolant in my resevoir when before I had hardly any. I take this as a sign of high pressure in the system (blockage maybe?). If anyone has an idea of what causes my problem then please feel free to chime in.

 

i would drain it, run water though the whole thing and see if you find any clogged up areas. if not, drain all the water and put the right amount of coolant and water back in it. the thing just might need a radiator flush. mine was kinda like that but i kept having to refill it like everyday until i did a flush and now it hasn't even gotten close to the halfway mark on my temp gauge.

 

actually it's the lower rad hose. check the lower rad hose see if it gets hot. if not it's your thermostat causing you to overheat.

 

I was just reading the hayne's manual I have here but quite often they are found to be mixed up. I also felt the lower hose and that was warm as well...I'll try the radiator flush and see what happens.

 

you're saying the needle goes halfway and doesn't like to come down?
does it go into the red?

 

It did it once about two weeks ago. It's originally at 1/4 normal operating temp. The time two weeks ago it would fluctuate from 1/4 to half rapidly. Then today it just skipped from 1/4 then up to 3/4 and wouldn't go below half.

 

if it is the same as my experience, there is a small crack in the top tank of the rad or the bottom tank.
somewhere in time the manufacturers went to plastic for the tanks and they develop small cracks.