Before ya take the head off, just do a quick compression check. Will tell you volumes.

There's also a check you can do via the radiator, but I always forget what it is. Google that one, I guess.

Could be a leaky water pump? Not sure if the 2.0 is like the 2.6 and will allow water to run under the timing cover into the pan? Think that engine is a belt-timed engine, so mebbe not...