What's probably wrong with my 2000 Chevy Malibu?

Car turns on then (there is anti-freeze in radiator) goes above the normal temperature range on gauge and starts to make noise. I stop the car. After going home and letting it sit a while ( I live in the Midwest) it turns on and goes to slightly below normal temperature and starts to heat car but it sometimes is... show more Car turns on then (there is anti-freeze in radiator) goes above the normal temperature range on gauge and starts to make noise. I stop the car.

After going home and letting it sit a while ( I live in the Midwest) it turns on and goes to slightly below normal temperature and starts to heat car but it sometimes is not warm but cool.

Mechanic said something about "air pockets".
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