Don’t just turn up the music and tune out the noise. If you car is emitting these screeches, howls, and groans, then it needs some attention right now.
1. A Diesel-Like Clattering in Your Gas-Powered Car.
Worst-Case Scenario: Detonation, also known as pinging or knock.
Why: Things like bad gasoline or incorrect ignition timing cause the fuel to go boom too early. If left unchecked, you risk serious engine damage.
What To Do: Switch to higher octane gas, which resists detonation, and check the timing.
2. Questlove Drumming Underneath Your Car when It’s Moving, Increasing with Vehicle (Not Engine) Speed.
Worst-Case Scenario: Failing universal joint or driveshaft bushing.
Bad Stuff That Can Happen: U-joint fails completely, driveshaft digs into pavement, and the car pole-vaults and crashes.
Why: Both the U-joint and bushings simply wear out. The noise comes from the driveshaft flopping around like an ailing fish.
What To Do: Inspect the driveshaft for worn or broken parts, replace them, or get to a mechanic.
3. A Million Fingernails Scraping on a Chalkboard when You Start Up the Engine or Accelerate from a Stop.
Worst-Case Scenario: Loose accessory drive belt.
Bad Stuff That Can Happen: Your enraged neighbors will kill you.
Why: The belt is slipping on the pulleys, either due to age and wear, or improper tension.
What To Do: Inspect the belt for minor cracks or fraying. Replace as needed.
4. Sharp Tapping Like a Clunky Washing Machine, Increasing with Engine RPM.
Worst-Case Scenario: Connecting-rod knock.
Bad Stuff That Can Happen: Broken rod blasts hole through the engine block; metal parts and flaming oil shoot out.
Why: Usually a failure of a rod bearing due to oil starvation.
What To Do: Stop driving immediately. If caught early, the bearing can be replaced.
5. Grinding Metal—Think Snowplow on Pavement.
Worst-Case Scenario:Brake pad or shoe material completely gone.
Bad Stuff That Can Happen: Destroyed brake rotors or drums. Car may pull to one side under braking and possibly crash.
Why: Brake pads should make a squeal when the pad has worn down to the danger zone. But sometimes we don’t notice this sound.
What To Do: Fix the brakes.
6. A Whine Like an Empty Ice Machine When You Turn the Steering Wheel, Especially at Low Speed.
Worst-Case Scenario:Failing power-steering pump.
Bad Stuff That Can Happen: Loss of steering assistance.
Why: Low power-steering fluid or a pump groaning to death.
What To Do: Check the fluid level, top off as needed, and get ready to buy a new pump.
Adopted from http://www.popularmechanics.com/cars/how-to/a10483/6-car-sounds-you-should-not-ignore-16793559/