A while back my R17 blew a head gasket in a big way. Puffing steam out of the oil filler, sump full of water/oil - the whole shebang.
Unfortunately the house renos were in full swing and the best I could do was to park the car in the shed and add it to the 'to do' list. Time ticked on and I dreaded the job more and more as the images of an engine caked full of rust and what was a simple gasket replacement and some head work looked like becoming a complete rebuild.
I sucked it up, started the job, then popped a hernia and was laid up in the time I wanted to fix the car. My imaginings went from bad to worse. Finally, I pulled the engine out the head came off, and to my great relief, the engine was - apart from sludge where you’d expect it - as clean as a whistle.
I realised that the coolant wasn’t water in the usual sense and the corrosion inhibitors had done their job.
Even better the motor looked like it had been only recently rebuilt, unfortunately some pre-existing corrosoin in the head wasn't addressed during that re-build but would be an easy fix nonetheless.
Slap a gasket on, discard the harmonic balance, put an R16 timing cover on it and it would be good to go.
(Oh and replace the transmission hump, address the leaking brake master cylinder, respray the engine bay and underbody, and... and...)