Radiator won't burp?

Best thing I can say is to do the following: With engine cold, remove the radiator cap. Turn heater on highest heat setting and heater in on position. Let the engine run until it has heated up and the thermostat has opened. Continue to let it run with the cap off and observe if any fluid addition is necessary. It's possible you broke some stuff loose when draining and flushing that has clogged the heater core. In this case, a reverse flush of the core is your best bet. Prestone makes a kit that makes this pretty easy. Apologies if you've already done this, but it's really the most expedient way I know how to get air bubbles out of a cooling system.

Same thing happened with my 99. Remove the two hoses going to the heater core from under the hood. Use a small piece of the proper size hose and connect with a hose clamp to the return side. Attached garden hose to other end. Flush backward. Make sure setting inside vehicle is set to hot. You may have a diverter that opens and closes when the setting is placed to hot. Make sure it fully opens and closes. You may have crud jammed up in there also.