over heating,not my mopar tho

Sorry this is not a mopar topic,its my 99 sun fire with the 2200 4 banger.Whats happening is after about 10 minutes of driving my temp goes up very close to the yellow range and pretty much stays there even at high way speeds and in stop and go traffic.Yesterday as it was slowly geting up there we heard coolant being pushed into the over flow tank,its done this a few times now,and when we got home sure enough the tank was full and flowing out the over flow hose on the ground.I have lots of heat,no coolant in the oil,and no white steamy exhaust,also my electric fan does come on as it should.When its as hot as its getting my upper and lower ho sees are not swelled up from pressure.May be its the cap or head gasket or dang.bad timing for sure this Wednesday I have to take Cindy to her eye appointment some 60 miles away.Looks like we may have to take it to a shop,how do they find whats wrong,in the cooling system,i sure don't want to throw parts at this car that's not needed.Thanksss in advance fore ant help.