My '94 V6 (3VZE) has developed an odd coolant leak on the passenger side of the engine towards the front. It is coming from an area hidden behind the compressor and it only seems to leak when the truck hasn't run for a day - I'll find a small puddle of coolant under the truck the day after using it. I can't see or feel the area where the leak is coming from.

I can't think of anything that would leak on that side of the engine except the water pump, which I had replaced last year with the timing belt. But, before I start taking things apart - are there any other potential sources of coolant in that area? Anything that might track with leaking only when the engine is cold?