[lutronjim]

I had a similar situation. Losing coolant but never saw any coolant. I could sometimes smell the antifreeze but never saw any.

Pressure test showed it was loosing pressure but no coolant could be seen. Scared to death it might be cracked heats or block. Ran a compression test and all was fine.

Finally bought dye kit from Summit. Turned out that there was a leak above the coolant level where core met tank - was a crossflow radiator. No fluid would leak until thermostat opened and flow would blow coolant out hole. Of course it was nice and hot and it would evaporate before you could see the coolant.