Beware of any and all holes, passages, and crevices in a hibernating 4x4. It's not just dirt that gets in. We should've gone straight to a radiator shop when we found the first traces of a rat's nest (in hand) in the top tank. But misers that we are, we fished out as much nest as we could with our fingers and coat-hanger wire, then flushed the radiator with water. We hoped any leftover lint would help plug pinholes but wouldn't clog the main passages. The engine runs cool; guess we got lucky.