'97 200SX SE-R Burning Coolant - Long

[Matthew Hartka]

I've searched the archives, but haven't found anything related to the
problem I'm experiencing.

My car started burning coolant about a month ago.  It was blowing smoke
and emptying the overflow tank (drawing it into the engine) every 25-30
miles.  I took the car to my mechanic, he pressurized the cooling system
(with the engine warm and cold) but he didn't notice a drop in pressure
and it never burned coolant for him.  At this point the problem was
intermittent, happening once a week.  This week it has started burning
coolant everyday.  It only blows visible smoke until the engine temp
gauge assumes it's normal position (roughly 8 to 9 o'clock on the
gauge).  After it's warm it still burns coolant, the overflow tank
continues to drop slowly and I can smell a faint coolant odor when I come
to a stop.  The strange part is, after I stop the engine it continues to
draw in coolant from the overflow tank (between 1/4 to 1/2 the tank)
until it is completely cool.  Last night, as an experiment, I pulled the
radiator cap as soon as I shut off the engine and it still drained about
a 1/4 of the overflow tank.  This week the car is slow to start and runs
rough until it is warm (and seemingly burned off the built up coolant),
then it runs normally.

Could this be the head gasket?  The gasket between the intake manifold
and the block?  Anything else that is coolant filled and upstream of the
pistons?