I can't find a drain petcock on the radiator for my 2002 4 cylinder 5 speed Frontier. Am I not seeing it? If there isn't one, do you know the best way to drain the coolant? I have 38k on the truck and would like to put in a fresh mix of Prestone and distilled water before the snow flies. I tried another Nissan forum site and nobody replied. Thought I'd try this one. Thanks!