nice having that shop on base isn't it?
jeep used radiators with plastic tanks on them and if i remember correctly, and being a child of the 60's i don't allways, the wj tanks are on the sides of the core. after pressurizing many thousands of times the little "fingers" that hold the tanks on get loose and you get a leak. tightening the fingers is only a short term fix as the metal fatigue can't be reversed. if you need a new radiator try performanceradiator.com. they have a warehouse here in town on south arville and usually have a good supply of jeep radiators in stock. i'm running one of theirs in my yj since 2000, steel tanks but i don't know if those are an option for the grands. fyi i had an xj with a leaky tank on a trail ride and we tossed in a tube of stops leaks and he drove it on the trail and for a month before he replaced it.