88 camaro 2.8 overheating probs

My 88 camaro is air conditioned and every thing works fine for about 30 mins and then I notice the air is blowing warmer and the water temp is rising. I have replaced radiator fan switch and coolant temp switch as well as the radiator fan relay with the same results. I have recently wired the fan motor direct with a switch for manual on and off and have had no problems with overheating but would like to fix it right. This camaro has a 87 build date but 88 on the registration. I don't have much experence with 2.8's mostly V8s. Also the car sat for a couple of years before I got it. Any help would be greatly apprecited, Jerry

does the fan work properly? come on when the a/c is on when the car is cold? leave the ac off and see if it comes on at about 200 degrees if it does a cooling system flush will probably help you out.. the radiator could be a little plugged

Consider replacing the thermostat with a 180 degree unit.

check for blockages in between the radiator and condencer, leaves, plastic bags, ect. check for fan operation, coolant level, and such.

flush the whole coolant system and make sure the thermostat is operating correctly. worst case scenario is a head gasket is startin to go. that happened on my moms firebird's 3rd engine. just make sure fans, thermostat, and fluid level and try flushin it a few times. should help ya out

Thanks, Guys !!!!
I have read and done most all the suguestions except the rad flush. I will do that on Sunday. thanks again for all the help Jerry