I purchased a ford F350 Harley Davidson long bed with 6.0 PSD in August of 2006, the build date on the truck is 4-2006. I ran the truck for 3000 miles changed the oil then placed the Hypertech chip stage 3 program in the truck. The truck did fine for a few months I pulled a 7500 lb travel trailer about 900 miles on stage 3 because hypertech claims I am able to with no tow restrictions, I don't have a pyro sensor and now it seems dumb to do what I did just because hypertech says I can. Now my truck spews coolant only with chip in the truck. I take the chip out and no problem. I took my chip out and took it to the dealer and they did a pressure test and it came out fine, I paid $8 for a new cap and still same problem. If I change chips will I have same problem? Is my problem more likely the EGR cooler or head gasket leak? I am inclined to believe it is the EGR cooler although my problem did not happen immediatly after placing the chip in it seemed to sneek up a couple of months after puting it in, this makes me question the head gaskets starting with a small leak and progressing to a larger leak maybe sometime progressing to a leak when in stock mode. What should I do next?

 

I doubt it's a head gasket. A leak in a head gasket would not fix itself when you removed the chip.