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Mechanic's Corner

Common Noises of Impending Car Trouble

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Picture yourself driving down the road on a dark and stormy night. Suddenly you hear a strange knocking noise that fills you with dread. Could it be … gasp … your car? You ask yourself: What is it? Can I make it to my destination? How much will it cost to fix?

Noises are your vehicle’s way of communicating with you. Ignore your vehicle’s message too long and it could lead to a breakdown and a big repair bill.

We don’t want that to happen to you, so here are some answers to the most common questions about vehicle noises and what they mean.

Q: What does a squealing or scraping sound indicate when I apply the brakes?

Most likely your brake pads are worn and allowing their wear indicators or sensor to touch the disc brake rotor. When this occurs, the sensor emits that high pitch noise to warn you that your brakes need attention. Have them checked out sooner rather than later before expensive damage or brake failure occurs.

Q: Why does my car make a knocking or pinging noise when I accelerate or climb a hill?

This is a sign that the gas and air mixture in your car’s cylinders isn’t burning properly. The sound you hear is the result of the fuel and air mixture combusting unevenly in the cylinder. Pinging or knocking does reduce the efficiency of your engine and over a very long period of time, it can cause damage.

Q: Why is my van making a chirping sound?

A cyclic chirping sound from the vicinity of a wheel often indicates a wheel bearing or axle bearing that is failing. Usually the noise will change with the speed of the vehicle. It may come and go at various speeds. This noise should not be ignored because if the bearing fails, it may cause the wheel to lock up or come loose from your car!

Q: What is that hissing sound coming from under the hood?

If you hear a hissing sound while driving or after turning the engine off, accompanied by a sweet, sickly odor, it may mean your engine is overheating and/or leaking coolant from the cooling system. The temperature gauge or temperature warning light should also indicate an overheating condition. Steam may also rise from under the hood. You should stop driving as severe overheating can damage your engine. Carefully open the hood. Look for any evidence of coolant leaking from the engine, radiator, or heater hoses. If you see steam or smell a sweet odor, it is antifreeze leaking from the cooling system. DO NOT open the radiator or coolant reservoir cap or add coolant until the engine has cooled. Get this checked out right away.

Q: What is that clicking or tapping noise from the engine?

A metallic tapping or clicking sound means your engine may be low on oil, or is not developing normal oil pressure. The clicking noise is coming from the valve train. If the oil pressure is low due to a low oil level in the crankcase, or there is a problem with the oil pump, the hydraulic lifters that open and close the valves may collapse, creating an increase in valve lash. This creates the clicking or tapping noise. Stop the engine, let it sit a few minutes (so the oil can run back down into the crankcase), and then check the oil level on the dipstick. If low, add oil as needed to bring the level back up to the full mark. If the noise does not go away, and/or the oil pressure gauge or warning light indicates low oil pressure, it’s not a good idea to keep driving your vehicle. Loss of oil pressure can cause extensive and expensive engine damage.

Q: Why is my exhaust system roaring?

If your exhaust system has a leak, you will hear a roar coming from under your vehicle that is loudest when accelerating. The noise means your exhaust system needs repairs. It is extremely dangerous if the leaking exhaust gases, which contain carbon monoxide, get inside the passenger compartment. Carbon monoxide (CO) is a silent killer. It takes only a small amount of carbon monoxide inside the passenger compartment to affect your alertness and your ability to concentrate and react to changing driving conditions. A very small amount can cause dizziness, headaches, nausea, and bring on stupor in two hours. A 1 percent concentration of carbon monoxide can kill a person in less than three minutes!

Q: Why do my tires make a thumping noise?

You may have a tire out of balance. This causes it to impact with road in a slapping sort of manner, causing the thumping noise. Get it looked at as soon as possible, as a neglected tire causes flat spots and eventually ruins the tire.

If you experience any of these warning signs, call your car care provider today and get it taken care of before it becomes a major repair. A call now will save you time and money.

Happy Motoring!

Add a Comment (1) Comments
  • Chris Leger, February 25, 2012, 09:21
     Enthusiast

    After having the differential and transmission oils changed at 45000 miles on my mercedes SL500, I notice a "whining " noise when I accelerate to about 30-50 mph and then let up off the accelerator. Never noticed this before . I also feel a sort of vibration at center of the floor with this "whining" noise. Could it be a problem with the driveshaft flex discs or something else? I'm going to get the oil changed in another 1000 miles but hopefully driving the car won't cause damage. Also had the ball joint replaced but don't see how this would cause that noise/vibration.

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