It has been abnormally cold here and when engine is warmed up at first it will blow heat, then head down the road and goes to cold then it will warm up again, then cold then warm. Some info, EGR delete was done and new radiator. Just put in new t-stat thinking that was the problem as when degas bottle it at correct level it will push antifreeze out the cap. Any suggestions on what to do next? Is it possible it is a vacuum issue as the auto-hubs aren't working right now either and when I put it in 4WD it will blow the air out the defrost for awhile then switch back? I had that issue before and replaced the vacuum pump a couple of years ago. I still can't quite figure out why that would cause the antifreeze to push out from the degas bottle. Bad cap maybe?

Thanks in advance for any help.

 

Since you have done the egr delete I would start with checking coolant pressure in the return line to the degas bottle. You can run a gauge to the inside if the cab and check pressure once fully warmed up and check it at wot. Anything over 16lbs you got head gasket problems which could be your issue with the heat and the degas puking.