Car repair can kill a student's semester at college

It's the sound every college student dreads:

RUH-TUNKTUNK TUNKTUNKTUNK TUNKTUNK TUNK...

What is it? I actually have no idea, and neither do you. And trust me, neither do the "Car Talk" guys, either: How many centuries has it been since they were in college?

Anyway there it is, clamoring underneath the hood of your car like a pissed-off zombie with a hangover. And you sure didn't hear it yesterday. Now the sole thought you can muster is, "Will this cost me $50 or $5,000?"