I replaced my headlights and they keep filling up with water. Anyone have any good ideas how to stop this? I hear it's a common problem when replacing the entire assembly.

 

This is a common issue with the less expensive headlight tail light assembly. A while back I purchased a set of tail lights from eBay at half the cost of factory style lights... They constantly build up condensation... Take them off and set them in the sun or use a blow dryer to evaporate the moisture... Take some clear RTV and create a seamless bead around the perimeter of the headlamp ( where it is already glued to the plastic housing ) allow it to cure and be certain your bulb connections have a good seal. This should do the trick!

 

could drilling a small drip hole in the bottom mess anything up?

 

Thanks for the ideas, I'm going to take them out and see what I can do