After I tracked down coolant leaking from lower radiator hose that was skewed, I still was losing coolant.

Coolant seeping out during the night only. Stopped by my mechanic's shop and they recommended Irontite. They had used it on a 240 that was spitting out visibly while the car was running. Leaked stopped by the time the Irontite had been poured into the radiator.

I used half a bottle (not sure why) of Blue version (not Red) per my mechanic's advice. Disconnected expansion tank relief hose at radiator (tiny hose). Attached a funnel to a 1/4" hose, then attached it where relief hose was. This prevents the goop from mucking up reservoir tank. Ran car for five minutes (I think car was running when pouring too). Mechanic recommended adding goop while car was warmed-up and it was. Next morning no coolant on driveway, and engine block had a white, dry residue from where coolant seeped.

I did this at the beginning of August and I haven't had any further leaks or other problems.

At under $20 a bottle, this stuff beats a head gasket at $1500 plus. If it can hold back that job another 1-2 years I'm happy...

In Portland, I got stuff at Bearing Service in NW Pearl area.