Paying for car repairs isn't the worst thing in the world . . . getting in a crash because you DIDN'T pay for repairs is worse. Here's a list of six car sounds that might mean a crash is in your future . . . so DON'T ignore them.
1. Diesel-like clattering in a gasoline engine. It could be bad gasoline, or your ignition timing might be off. Either one could cause serious engine damage if it isn't fixed.
2. Drumming underneath the car that increases with speed. It could be a failing U-joint. The worst that can happen is that the U-joint breaks, the driveshaft hits the pavement . . . and your car flips end over end until something stops it.
3. A sound like fingernails scraping on a chalkboard. It's probably a loose accessory drive belt. It's not life or death, but everyone around you will hate you until you fix it.
4. Sharp tapping that increases with engine RPM. It could be a connecting rod knock. In the worst case, the rod punches through the engine block . . . metal parts and flaming oil shoot out . . . and you're shopping for a whole new engine.
5. Grinding metal, like a snowplow on a bare road. Your brake pads could be completely worn away, which could cause the car to pull to one side when you brake.
6. Whining when you turn the steering wheel. It could be a failing power-steering pump. If it failed completely, you'd lose your power steering . . . and you wouldn't know it until you tried to turn the wheel. (Yahoo! Autos)