i put a del sol radiator in my 91 civic and when it gets to normal driving tempature and i turn my fan on and the tempature drops all the way down as if it was really cold but turn fan off and starts going up to normal tempature is that normal or not??

 

You have a manual fan switch I take it.

Are you runnign a thermostat?

Did you get the single core or dual core radiator???

 

You radiator could be old, and obstruated

 

yes manual fan, no themostat and single core fan i think??

 

No thermostat is a BAAAD idea. It's a restriction in your system, yes, but it serves dual purposes. Slowing the flow down lets it cool down in the radiator. If it's flowing too quickly there's not going to be much cooling going on, or so all the v8 guys have told me.

 

The thermostat makes sure that your engine heats up to the proper temperature. An engine operates at it's best when it's at it's optimal temperature. Not running a thermostat is a bad idea.