Cadillac Repair: engine running hot, engine coolant, head bolts

Question
i am working on a 2000 cad. deville. it has the northstar engine, first the radiator was cracked so i replaced that,it ran good for a week ,then started running hot again, i checked the thermostat and repplaced that, it ran great for 3 days now running hot again.i am at a lost now..

Answer
When you replaced the radiator did you install a new one or a junk yard one ?.

Your problem is most likely the ever well known very common with this engine whih develops leaks in the HEAD GASKETS due to the steel head bolts stretching the threads in the ALUMINUM engine block which causes a pressure buildup within the cooling system which prevents the engine coolant from flowing thru the engine in order to keep it cool.

Some people have resolved their problem by installing the CADILLAC SEALING PELLETS into the radiator of which you can purchase at any auto parts store. This MAY or may NOT work but it is worth a try.

Otherwise you have to remove both cylinder heads and install heli-coils in the engine block and install all new head bolts.