I think I may have penetrated the water jacket when repairing the stripped exhaust header bolt holes on the head of my 1.9l wasserboxer a few months ago. Next steps? remove the headers (again ugh!) and determine if I can visually make out where the leak is. Failing that drop the engine for a better look or maybe pressurize the coolant system and see where it is leaking? Any suggestions welcome.

Here is the detail of the goring I managed -

After successfully (thanks to the fine people on this list) repairing stripped threads securing the power steering pump I got bold and went after the exhaust header bolts with the engine in. There was just enough room to fit the drill in there. The new threads went in fine and the exhaust was amazingly quiet. I left for a trip into the hill country and drove all weekend without incident. The van sat for a while as I worked through replacing the ac lines. When I started it up quite a bit of water came out of the exhaust pipe. Not good. Enough water to puddle the driveway. The engine ran fine and the plugs weren't fouled or rusty leading me to believe that the penetration happened only on the exhaust side. 

84 Westy 1.9l wasserboxer
Owen Brand