satellite in the L4 or L5 point (Earth-Moon system) would never "eclipse" the Sun because it's far far far smaller than the Sun's disk, seen from Earth. Besides, as Dan points out, the Moon orbit around the Earth (and L4 and L5 orbits too), is about 5 degrees away from the ecliptic point (and therefore, entering the Sun's disk would only occure around a few times a year).
Another thing: entering the Sun's disk and leaving it would take about 1 hour: that's the time it takes an object at the Moon's distance to cross the sky in a distance equivalent to either the Moon's diameter or the Sun's diameter (as seen from Earth) or about 31 arc minutes.

Raoul