Check the oil. If the water is escaping the motor, it
can only go a couple places and the sump is a common one.

Is it a fuel injected or carbed car? The carbed cars are
more prone to overheating.

My car was quite prone to overheating until I replaced the
t-stat with a 160 degree unit and recored the radiator. It
still sometimes runs a bit on the warm side.

If you did overheat your motor, you may have blown the head
gasket and very likely warped the intake/exhaust manifold if
it is carbed. None of this stuff is very hard to fix or very
expensive.
chris