I purchased my 08' 4.0 Sport Trac last Saturday and drove it home 100 miles with no problems, no nothing. Popped the hood, checked all fluuds, all good, no leaks. Went to Autozone, purchased a 16 lb radiator cap, swapped out the 20 lb cap in a cold engine and started it. At operating temperature (gauge needle @ slight less than mid way) and I smell antifreeze. Look under the hood and behold, small leak in top of radiator (plastic). Attachment shows where leak was.. An @ 2" crack in the middle two squares (I epoxied beyond the crack either side an additional couple of inches for what I couldn't see was a crack but expected to be a crack at some point. Thing is, when I got the cap the store had two versions, one with no pressure spec stamped in the cap, and another with pressure relief valve and 16 lb stamped in the head of the cap. I bought the latter. Shame on me, I should have tested the cap unfortunately my Stant coolant tester did not have the correct adapter and 0'Reillys wanted $200 bucks plus tax (rental) for me to test the cap even though I could test it over the counter and hand the tester back to them. Went back to Autozone, had them pull out the other cap and three of us tested physical pressure pushing the springs for comparison. We all agreed the unmarked cap definetely required less pressure. So now I am doing a repair (see pic) to see if it actually works while I search listings for an all aluminum radiator. Btw, I'm using JBWeld Plastweld for the repair (all I could find locally otc). Pic shows first application, I plan a second, final coating after the first cures. Anyone recommend a reasonably priced all aluminum radiator for the 2008 ST 4.0? I see one on Fleabay for @200 shipped. From California so I'm sure it's off the slow boat from China..