I suspect the radiator is cracked somewhere.  Anyone have any experience with this sort of thing?  Can this do damage to the engine block?  The radiator is custom and will not be cheap to replace, and it will take a while, and the plane is an 8 hour drive away...  :-(

The leak you can see is the best kind. Aluminum radiators can be TIG welded or epoxied and still work fine.

 

If it were me, I would strip off the front cover and inspect the core support plugs in the front iron. They usually push out first in a hard freeze. That dumps coolant into the oil pan and destroys the bearings in just a few seconds at power.

 

If a plug has moved, take it out. Install a new plug. If you are not sure about any of them, do them all.

 

On piston engines, we used to drill and tap a hole beside the core support holes and install a 10-32 socket head screw and a washer that extended over the edge of the hole on two sides. Threading the hole and installing a plug would work also.

 

Lynn E. Hanover