I have diesel in my coolant on my 2004 f350 6.0. was told that i may have a crack above the injector cup. No testing has been done yet. Is this the only thing that can cause this and how can I test for this problem. I have had egr cooler replaced about 20000 miles ago and also 2 injectors about 10000 ago by ford and cant really afford to take it back to them again. any advise greatly appreciated. thanks darrell