In Star Trek 3, the Enterprise is set to self-destruct and abandoned before the Klingons board her. They get to the bridge and hear the self-destruct countdown. None of them think this is a problem, until their commander hears it and puts together what's happening. Too late.
Why don't the Klingons recognize a countdown on an abandoned ship being a Bad Thing? Do they have no concept of self-destruct, or of countdowns? Maybe Kruge is the only one who spoke English, and they didn't have universal translators? (In which case, their conversations were just being translated to English for our benefit?) Or is his crew just dumb?