You could have air. What year?? check the level when cold. remove the cap from the expansion tank and let the engine run up to temp. Turn on the A/C. Watch the temp and make sure your fans are coming on. Rev it a bit and listen to see if the fan clutch is OK. If the level is correct and it doesn't boil over w/o the cap, depending on the year, you may have crud in the rad or a reluctant thermostat.

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Jeff Lawrence
1989 300e
2000 Dodge Grand Caravan SE
No matter what you fix, there will always be something else to fix..
"Warranty" is just another way of postponing the inevitable.