When poking around the van a couple of days ago, I noticed an odd puddle under the engine:
It seems to be a coolant leak. Very odd though, the van has just been sitting in the shed for the winter, hasn't been running since November. We've had a couple of very cold days recently though.
The dealer couldn't diagnose it from the pictures I sent, so I'll be taking the van in next week, weather permitting, and hopefully it will get resolved. I sure wouldn't start south with a problem like this lurking.