I paid $300 and change back in 94-95 time frame on my mustang. No clue what it would cost for a Jeep. Don't think there's anything you can do for a bad core other than replace it. You need to take it to a mechanic to get it checked out and get an estimate. If you can't diagnose / fix the issue yourself.I do smell some anti-freeze. Looks like that could be it. Are there any sealants or additives I can use to try and plug the leak? If not, what can I expect to pay to get that replaced?