Get ahold of a cooling system pressure tester. You then pump pressure into the cooling system and watch the pressure gauge. If it slowly drops, there is a leak somewhere. Then test the cap. New caps ate notorious for being bad...especially the cheaper ones
91 YJ Sahara, 4.0L, AX-15/NP231, D30/D35@3.07
12 Cherokee 4x4,3.7L,42RLE/MP1522, D30Memail@example.com
"Non Vi Sed, Arte"