Our Caravan has loss antifreeze every 3 or 4 months for the past two years,with no puddles in the driveway or wet spots on engine. Last month after an ice storm my brother-in-law noticed a puddle when we were warming it up. He took the Caraven to a mechanic friend of his who could not find a leek, but recomended replacing the 16 lb radiator cap with a 13 lb cap. we are still loosing antifreeze, but still cannot find where. There is no oil in the radiator or water fouled sparkplugs.
Which engine do you have? It does make a difference.
I currently have a tiny radiator leak - it drips only while the engine is cold and running, but doesn’t seem to leak at all when the engine is hot. The only way I even figured it out was - a) having to add a pint or so every couple/few months, and b) I do a lot of my own maintenance/repair so when I start the car cold & put it up on ramps or jack stands I find it dripping then. Perhaps ask your mechanic to make sure s/he starts the engine from dead cold to look for a leak (or you can).
I had a situation similar to Cigroller once: a water pump that dripped only for a short time while the engine warmed up. I spotted it while fiddling with the fast idle mechanism on the carburetor.
the engine is a 3.0 ltr