How much coolant are you losing? I once had a problem with a mini van losing coolant over a longer period of time and it turned out to be a bad return line to the overflow. That was cheep to fix. Hard to find though. The way I was able to find it was by driving it to full operating temp and the park in the garage with the hood up, engine off and overhead door shut (to eliminate any breeze) shine a bright flashlight with a tight beam around the engine bay looking for a small/weak plume of steam.
Any white smoke from the exhaust? If so, your getting it into the combustion chamber or exhaust port. That would be bad.
My
, good luck.