If you’re not exactly mechanically inclined, the only sure-fire way to find out why your car is making a horrible noise is to take it to a mechanic for a diagnostic. But if you’re still curious, you can do a little do-it-yourself investigation. A grinding noise is most frequently associated with problems with brakes, wheel bearings, water pumps, alternators and power steering pumps.
Start the car. If the grinding noise starts right away or is present anytime the engine is running, pop the hood. If the grinding hasn’t started yet, skip to step three.
Open the hood. If you can’t identify the alternator, water pump and power steering pump, refer to your car’s owner's manual until you know what’s what. Take a piece of hose and put one end up to your ear. Point the other end at the alternator, then at the water pump, and finally at the power steering pump to see if you can pinpoint the source of the noise. If any one of these three is the culprit, that part will likely need repair or replacement.
Start driving. Listen carefully when you touch the brakes. If the grinding occurs when you brake lightly and worsens when you brake harder, you may have worn brake pads. This is easy to confirm; simply look at the brake pads to see how much thickness is left. If you’re down to within the last quarter inch, it’s about time for a replacement. If you’re not sure what the brake pad looks like, again, consult your owner’s manual.
Continue driving if the brakes are not the source of the noise. Make both a right turn and a left turn. If you hear the noise only when making one of these turns or the noise worsens when you make a turn, the problem is likely to be a wheel bearing. If turning one direction makes the noise louder and turning the other direction makes it quieter or makes it go away entirely, it is almost certainly a wheel bearing. This is a huge safety issue which must be dealt with immediately by a professional mechanic.
Take the car to a mechanic if you do not have the skills or tools to repair the car yourself, or if you cannot pinpoint the source of the grinding noise. Look for a mechanic that will apply your diagnostic fee to your repairs to get a good deal.
