You could try the "De-Tango" method to get inside the lights, if you want to clean them.
http://www.projectpuma.com/viewtopic.php?p=16025#p16025" onclick="window.open(this.href);return false;
Otherwise, Colin (BOK), sadly, no longer with us, used to swear by this product for sealing, without dismantling:
http://www.captaintolley.com/" onclick="window.open(this.href);return false;
http://www.amazon.co.uk/Captain-Tolleys-Creeping-sealer-250ml/dp/B002EP4ROY" onclick="window.open(this.href);return false;