Cadillac Repair: 1995 Cadillac STS has combustion leak, engine coolant, cadillac sts

Question
QUESTION: I am having trouble with this car my wife decided to buy.  It is in perfect condition on the outside and the engine looks great, but it seems to be having a combustion leak into the cooling system.  I did a combustion leak test and it confirms it.  The car is overheating and have done almost everything I know.  I have changed the thermostat, checked all hoses flushed the radiator.  No water has leaked into the engine yet, and no white smoke is coming the exhaust, I even disconnected the catalytic converter to see is if was clogged but did not work.  Also I noticed that the reservoir cap is 16 psi and the manual ask for a 15 psi, don't know if it is that big of a difference.  Hopefully you can help, I also tried a head gasket sealer but has not worked.

ANSWER: Put about 80 lbs of constant air pressure into each combustion chamber with the sparks plugs out and see if you get bubbling of the engine coolant thru the radiator cap opening. This would confirm faulty head gaskets which is very common on these engines.

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QUESTION: Also I forgot to note on my last question that while the car reads a temp of 245 and up the engine does not seem hot and the coolant cap is also not hot I mean the engine seems to be a a warm temp but not hot like I have seen on overheating engines that you can't even touch with a wet rag.  And how much does it matter about the radiator cap not being the right psi.  Is there a quick fix so that I can sell the car and well not deal with the whole hassle of the head gaskets.

Answer
Usually the reason for putting on a higher pressure cap is to try and prevent the tension spring in the cap from opening and relieving the coolant back into the plastic overflow jug which eventually fills up and dumps the engine coolant on the ground from out the top of the overflow jug.

Not much you can do. Sell AS IS or replace gaskets.