personally dont know of any way to test a leak between coolant and oil passages like that other than the teardown.. i think no matter what you do, the problem lies in the engine so either way you'll have to tear down the intakes and get in there
2003 3.8L V6 4R70W
Windstar Upper Intake with cool-air intake, MAC LT headers, BBK O/R H-pipe, and flow 40s, SCT tuner, FRPP Alum. D/S, 3.73 gears, Auburn HP limited slip, and Team Z LCAs, Eibach sway bars.
Best 1/4 time: 15.036 @90.92mph, 2.148 60'