Cadillac Repair: 98 Caddilac SLS 4.6 liter V8, coolant system, head gaskets

Question
The engine overheats once in a while, and the heater doesn't put out any heat at all.  What should I try?  Also which hose off the radiator is the top and which is the bottom, as they both come off the top of the radiator, one on the left and one on the right?  Any help will be GREATLY appreciated.  Thanks, Gary

Answer
What you have is the ever common well known issue of leaking head gaskets which is allowing combustion pressure into the coolant system thus restricting the coolant flow.

This is  well known for this engine and year of vehicle.

You have only 2 choices. Replace the engine or sell it.