Got a car with a suspected hg. (Diag'ed by unknown mechanic) its a 93 civic ex.
However, I didnt see any of the telltale signs.

No coolant in oil
No oil in coolant (or milky cap)
No white smoke out of exhaust
No overheating (unless the water drops to next to nothing)
No coolant under waterpump or pully
No coolant leaks from heater core (Passenger side carpet is bone dryer
No air bubbles in radiator
Normal running condition

It does lose coolant about an overflow container a week worth. I dont see any leaks,
Thoughts? Headgasket? Waterpump?

 

I have the same problem as you with a 98 :/ but mine has Oil in the Coolant Resivour :/
I recommend just keep refilling it it may be just filling up space somewhere

 

how about a compression test? that would be a telltale sign.

 

use a coolant system pressure test, listen and look for where the coolant is going.