People sometimes don't listen to their cars -- even when they're trying hard to tell them something important. For example:
* Underhood screeches: Your engine bay's not Abu Graib and it shouldn't sound like it, either. If you hear screeching sounds when accelerating or turning the steering wheel, your car could be telling you it needs a new belt. Or the power steering reservoir might be low. It could also be a failing water pump. Don't just turn up the radio to drown out the noise.
* Undercar sputtering: If you suddenly begin hearing sounds of this kind, you've probably got a leaking exhaust system. Usually, the sound gets more obnoxious the harder you push on the gas pedal -- and when you suddenly lift off the gas, even more so. It's important to get this checked out as quickly as possible because a leaking exhaust system can allow dangerous fumes to seep into the car's interior -- in addition to annoying your neighbors.
* "Clunking" or "Ka-thumping": If, when you put your car in Drive, you hear a fairly loud clunking or ka-thumping sound, it's not the body in your trunk -- but more than likely worn-out universal joints. Let it go forever and eventually, the joint could fail -- and the driveshaft come loose, with potentially unpleasant results.
* Strange smells: Engine coolant has a very distinctive smell -- and if you've smelled it inside your car, you could have a real mess on your hands. A not-uncommon problem on older cars is a leaking heater core -- a small, radiator-like part buried deep inside your car's guts. When it fails, it can allow hot, smelly, disgusting engine coolant to seep into the car's interior, soaking the carpet and making your life very unpleasant. Another clue: The presence of an oily/foggy film on the inside surfaces of the windshield, right near the defroster ducts. Get thee to a shop, pronto.
* The drips: Babies leave clear signs it's time to change the diaper and in the same way, your car's leavings can clue you in to developing "issues." If you notice reddish-brown drips, it's a sign you may have a leaking transmission. Green-orange suggests cooling system trouble. As for oil (heavy, molasses-to-blackish colored goo) so long as it's just a few drips, it's probably nothing to worry about. All engines eventually drip a little. But when you see more than usual -- especially anything that could be described as a "puddle" -- you should have the car checked out right away. And be sure to top off the oil level before you drive anywhere -- and watch the oil pressure gauge as you go. If the pressure drops (or, on cars with just warning lights, the light suddenly comes on) stop the engine immediately and check/add oil. If the leak is severe (or you don't have any extra oil with you) either call a tow truck or go get some oil. Just don't run the engine -- unless you won't mind paying for a new one.
* Metallic tapping/clicking: If you hear a sound like this, it could mean you're low on engine oil. If you've checked the oil level and it's fine -- but the tapping/clicking sound won't go away -- you might have an out-of-adjustment valvetrain (or perhaps a collapsed lifter on non-overhead cam engines). In either case, the underlying cause should be investigated as soon as possible to avoid further damage -- and expense.
* Someone's knocking: If you ever hear really loud knocking sounds, it could be the funeral march/last words of your four-wheeled friend. These sounds are impossible to drown out -- and signal ugly, unpleasant things things like main bearing failure. If you shut down your engine immediately, you may limit the damage. But it's probably already too late.
