We’re buying a new car this weekend. I’m hoping the clunker we’re using for a trade-in doesn’t conk out before we get to the showroom, or drop its engine when the salesman opens the hood. The “Check Engine” light comes on randomly; no one at any garage seems to know how to fix it. If it’s not lit up when we get to the dealership, do we have to mention it? If the shoe were on the other foot, would the car dealer tell us? The clown who sold us the car didn’t mention that the windshield leaks when it …