Cadillac Repair: Cadillac deville overheating, radiator cap, head bolts

Question
QUESTION: I have a problem with my father in laws "99 Cadillac Deville 4.6L Northstar overheating. It does not lose coolant except when it overheats and pushes past the radiator cap. I did a compression test on the engine and got 175 psi on all cylinders, that coupled with no coolant/oil mixing should mean no bad head gasket (right?) The radiator, water pump and thermostat and radiator cap have all been replaced and seem to be working properly. I have done my absolute best to remove any air from the system.



I drove it last week and went 15+ minutes with no problems, engine temp running around 190-210 degrees. Roughly 10 miles including 3 or so on the interstate. Shortly after getting off the interstate the engine temp stated rising at all speeds including parked and idling. I shut it down at 160 degrees for 30+ minutes.  I then had to limp it the 5 miles back to my home stopping about 3 more times. Last night I drove it around for less than 5 minutes and the digital temp gauge hit 245.  

I am pretty much out of ideas.  Any help would be appreciated.



ANSWER: I have been out of town, Do you still need help ?.

---------- FOLLOW-UP ----------

QUESTION: Yes, please


Answer
This particular engine has head bolt problems that allows combustion chamber pressure from the cylinders to get into the coolant chambers of the cooling system which naturally stops the normal coolant flow and thus the engine overheats. This is a very common problem .

Try retorquing all your head bolts and see if any are stripped out.