This overheating issue has me baffled. I believe a possible head gasket leak now. When the car is warmed up you get that antifreeze smell, yet noe exterior visible leaks, yet it uses some coolant, seems to air lock in the circulation, so frequently bleeding to keep coolant flowing through especially in the interior heater. I think now that as the engine warms up there is a slight leak on one of the head gaskets that is oushing small amounts of air into the coolant side and then when the engine is shut off it leaks small amounts into a cylinder. This is the only left that I have not checked.

 

Did you check the oil color yet. If it is light brown don't run the engine until the gasket is repaired. I have the same engine in my 2000 s-type and over heating can warp the engine parts. Also the plastic "T" stack or thermostat housing can develope pin holes. Are you checking the exhaust for what seems like extra steam which would tell you if she is leaking coolant int the cylinder. Good luck in sniffing out this one.