Diagnose Problem By Listening

     Take the time to turn off the radio, turn off the air conditioner and roll down the windows.  Now listen!  Some sounds your car is making will let you know in advance what needs to be fixed.  Before you end up at the mechanics shop with a huge repair bill, or worse yet, stranded somewhere and having to walk to get help, just listen. 
     Some examples of the more common sounds you can hope not to hear include the following:


A grinding noise from under the hood when the engine is running.

With the engine still running, hold one end of a three foot length hose to your ear and the other end to the water pump.  Then listen to the alternator this way.  And the final possible suspect would be the power steering pump.  You should be able to tell which one is the source of the noise and needs some attention.

A grinding or rumbling noise from one of the four corners of the car.

This  probably means that a wheel bearing is going bad.  If the sound appears to be coming from the right or left side of the vehicle, it may get louder as you steer in that direction and temporarily increase the load on the bad wheel.  The noise may diminish as you steer away from its apparent source.  See a mechanic right away, or your wheel may fall off, or completely lock up.  Scary if your in traffic or traveling at high speed. 

A loud squealing noticeable immediately after starting.

This is almost always caused by a loose or worn-out drive belt.  In most cases adjusting or replacing one or more belts - a simple and inexpensive procedure - will solve the problem.

A knocking or "pinging" sound from the engine during acceleration.

This noise is often accompanied by a tendency for the engine to run on briefly after the ignition has been turned off.  This suggests that you may be using gasoline with too low an octane rating.  Try a tankful of higher-octane fuel and see if the problem goes away.  If it doesn't, see your mechanic.

A ticking , thumping or banging sound from the engine that becomes louder and faster as the engine speed increases.

This may be caused by problems with the valve lifters, pistons, connecting rods or a number of other things, all of which demand immediate attention if you hope to avoid major engine damage.  See mechanic immediately!!!

In a front-wheel drive car, a rapid clicking sound from one of the front wheels upon cornering.

This probably means that a constant velocity (CV) joint on that side of the car is worn.  If the rubber boots that protect the joints are intact and the noise can be heard only during tight turns, you can put off the repair for a while.  If the noise is continuous or audible during gentle turns, or if the rubber boots are torn, get to the mechanic asap.

source:  Yankee Magazine's Make It Last by Earl Proulx