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.
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.