On Philip's engine, the material of the heater pipes has been eaten way by hot, aerated water flow, leaving the pipes so much scrap.

Not sure if the water pump seal has failed, but the pump will be changed (4th one) before we run the engine.

I've seen this before on truck engines, but never as bad as this one, where the swaged pipe ends have holes eaten through, leaving a shiny polished surface.

Something to watch out for.

Peter