mktsc

On an average 70 degree day after about 1/2 hour of city driving, my temp gage is about 5/8 of the way up, and the hi-fan kicks on. This never happened when it was 50 degrees out, but now that it's a little warmer, the car heats up more. No problem, however my hi-fan kicks on whenever I drive alot in warmer weather. I recently replaced the coolant resevoir due to a hairline crack in it. Could it have introduced air into the coolant, and could this be causing the car to heat up more than it should?

Is this even a problem? Is the hi-fan supposed to kick on all the time?

-Matt