Cadillac Repair: 1999 Deville Overheating, bolt holes, coolant system

Question
I bought a 1999 Deville with 55,000 miles in January.  It has since overheated and all coolant gone.  Took it to a mechanic to Dx the problem.  He saw evidence of leakage from the lower hose and tightened it.  Ran fine for several weeks then did the same thing.  I had to be towed off the freeway.  The same mechanic "suggested" it is a head gasket and to think about what to do as it would cost 3k plus to repair that.  I see no puddles of coolant on the ground nor do I see "steam" from the exhaust.  Any ideas?

Answer
The most common problem with this engine is that combustion chamber pressure is getting into the coolant system because of stripped/stretched head bolts in the engine block. This is a very very common fault with this engine and requires drilling out all the head bolt holes in the engine block and installing STEEL HELI-COILS and different head bolts.

How Cadillac got away with making this lousy engine and not honoring their lousy design is beyond me.