[Lord of Hog]

Get yourself a dentists mirror too. That engine gets very warm and any escaping coolant not finding a nice little recess to accumulate in will evaporate quickly leaving a pale pink residue which can easily be confused with the normal oxidisation of the metal components.

I've had coolant leaks as a result of the following (all mercifully fixed now): compressed thermostat housing O-rings, incorrectly positioned thermostat straight pipe fixings, expansion chamber cap O-rings, cracked plastic elbows on the radiator, failed inlet manifold gaskets and of course good old perished coolant pipes.

In many of these cases what you're trying to see is cunningly concealed behind or beneath what it may be leaking from as a result of gravity and water's natural tendency to cling to suitable surfaces as it makes its way down.

Or of course it could simply be as Simon suggests and your cooling system has accumulated a lot of air bubbles