Zetec "sticking valve" issue.
Ford had a release about this years ago - I know because I went through exactly the same thing on my first car which was a 96 Escort Si.
The recommended solution was Forte engine flush, and a change to a different viscosity oil which solved the problem completely - this was actually recommended by Ford on their note to dealers at the time.
As for the fan thing, my guess is that it's unrelated, but still worth looking into.
Google the sticking valve thing - loads of info out there about it.