With all the discussion about cooling system effectiveness, Scirocco radiators, etc, I thought I'd post a picture of the original water pump I just took out of my 1980 X with 40k original miles (I have all the service records and it never had a water pump and it never overheated). I drove and raced this X with the water pump looking like this and it never overheated. Also, all that stuff is sludge, not corrosion, and it cleaned right off with a wire wheel (I still replaced it).
Dave
Dave