Cadillac Repair: overheating, bolt holes, head bolt

Question
my 96 caddy deville keeps overheating. have replaced the thermostat twice and bled the air out of the system. it will go for may be two weeks without overheating then overheats and all boils the antifreeze out of the overflow

Answer
This engine has a history of strpped head bolt threads in the aluminum engine block causing combustion pressure to get into the coolant chambers restricting the normal coolant flow.

You MUST drill out ALL the head bolt holes and install heli-coils and new head bolts in ALL the holes.