Only 2.5 gallons? Wow, should be closer to 4 gallons. To burp it, if you can find a place to park where the front end is elevated slightly higher it usually helps to force the air out radiator. Allow it to cool enough so you dont get burned by coolant when you take the cap off, then start it up. Turn the heater to max heat and fan to hi. Let it run and start to pull coolant through the system. Top off the radiator frequently, and squeeze the upper hose occasionally to push air out. The upper hose will be squishy while the cap is off due to lack of pressure in the system. When you cant add any more coolant to the radiator, put the cap on and let it idle to build pressure up. This is when the upper and lower hose should start firming up. Make sure you have coolant in the overflow tank as well, as the system will pull from there as it needs to. It will probably take anywhere from 15-30 minutes to get the trapped air out.
1995 ZJ 5.2L V8 318. 230,000 miles and still rollin.
List of parts not replaced yet: