[Khledar]

Just because they're from junkyard dont mean they're dirty, I've gotten some really clean ones, and a rinse will do, then there's the grimey ones. And the ones in disguise! Oh goodness, shiny on the outside.... Ugly on the inside. Try a rinse first, if you get grungy stuff try rinsing with steaming hot water, and if it wont rinse clean... You can try boiling it, and I'm sure there are some good grease cutters/etc that'll clean stuff up nice. But first try to figure out what's inside be it soil, oil, coolant, or whatever has gotten into it at the junkyard (or its past life). Best part about junkyard is the price, you can get a few for like $10 and maybe some will rinse out on the first go.