If you open the hood/bonnet in a modern car with a gasoline or diesel engine, you will see at least one serpentine belt, exceptions been electric cars as they have no belts. The job of a serpentine belt is to drive accessories installed on your engine such as an alternator, water pump and air conditioner compressor.
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| Serpentine belt |
A serpentine belt is different from a timing belt. A timing belt runs the engine camshaft(s) and is hidden under protective covers. A serpentine belt is located on the side of the engine and can be inspected from under the hood.
What Happens If A Serpentine Belt Breaks?
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| A broken serpentine belt |
If a serpentine belt breaks, a car won't be drivable and will have to be towed. If the engine runs without a serpentine belt, it might overheat as the water pump will no longer work. A broken belt can also damage other parts.
Symptoms of a broken serpentine belt include loud slapping, squealing or knocking noises coming from under the hood. The battery-shaped charging system warning light might also come on because the alternator will stop charging the battery. If a car has a hydraulic power steering pump, the steering will become stiff.
Common Belt and Tensioner Problems That Can Cause A Belt to Break or Produce Noises
Here are several common problems:
1. Regular Wear and Tear; A new serpentine belt has a soft felt-like surface on the ribbed side. As the belt wears out, the belt rubber hardens and cracks. A worn-out belt stretches and loses tension. This causes the belt to start slipping from time to time. You might hear it when the engine is started in the morning or in wet weather as squealing or chirping noises coming from under the hood.
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| Comparison between old and new serpentine belts |
If there are no other problems and the belt tensioner is in good shape, a new serpentine belt should fix this problem.
2. Oil Leaks; Sometimes, an engine develops oil leaks around the belt area, which causes the belt to get soaked in oil. Oil or coolant can damage the serpentine or timing belt fast.
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| An oil-soaked serpentine belt |
Belts sometimes last less than a week in an engine that leaks oil around the belt area. In this case, there is no point installing a new belt. The oil leaks have to be fixed first.
3. Bad spring-loaded automatic belt tensioner; Proper tension is vital for any belt. Often an old spring-loaded automatic belt tensioner seizes up or wears out and becomes weak. Without proper tension a serpentine belt will start slipping. This will cause the belt to wear faster.
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| An automatic spring-loaded belt tensioner |
Symptoms of a loose serpentine belt include a loud squealing noise when the engine is started or when the steering is turned all the way to one side. A serpentine belt that keeps slipping off the pulley is another symptom of a bad tensioner.
4. Problems With Hydraulic Belt Tensioner. Many cars have a hydraulic serpentine belt tensioner, where instead of the spring the tension is maintained by a little "shock absorber". It too can fail.
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| An automatic hydraulic belt tensioner |
Symptoms include a leak from the tensioner or a rattling noise from the belt area when the engine is running. This item is common to fail in many cars including Toyota Corolla, Matrix, BMW and Mazda cars.
A bad tensioner must be replaced. The belt should be replaced too, unless it's in like-new condition.
5. Manual Belt Tension Is Out of Adjustment. In some cars the belt tension is adjusted manually. Over time, the belt stretches and if the tension is not adjusted in time, the belt will start slipping. This is what happens when an older Japanese or Korean car makes a loud screeching noise when started.
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| Manual belt tension adjustment |
If the belt is still in good shape, the tension needs to be re-adjusted. If the belt is bad, it needs to be replaced and properly tightened.
6. Misaligned Belt Pulley. A serpentine belt runs on several pulleys. If any of the belt-driven devices or a tensioner pulley for some reason is not lined up with the belt, the belt will squeal. Often this problem is discovered after a newly replaced belt still squeals or wears out fast. One of the symptoms of this problem is increased wear on one side of the belt.
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| Misaligned alternator |
Sometimes, you can visually see when one of the pulleys is not lined up. The fix is to replace the belt and worn-out alternator bolts to align the alternator or the alternator bearing.
7. Noisy Idler Pulley or Tensioner Bearing. To route a serpentine belt, many cars use free-spinning pulleys like the one in the photo below. It's called an idler pulley. It spins on a little bearing. When that bearing goes bad, it can produce a whining/whirring or screeching noise. Because several belt-driven devices can make a similar noise, this one might take some time to diagnose.
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| Idler pulley |
A failed bearing in one of the idler pulleys like this one is another common source of the noise.
A bad bearing inside the alternator, A/C compressor or power steering pump produces the same type of noise. A mechanic might have to remove a belt and check the devices that are run by a belt one by one.
When a Serpentine Belt Needs To Be Replaced
A serpentine belt can last a very long time. It's recommended inspecting the belt during regular services.
Look for cracks, splits, damaged edges, missing chunks, glazing and other signs of wear. In most cases, it's easy to see when the belt is worn out. A worn-out belt must be replaced. A serpentine belt must also be replaced if it is found to be soaked in oil or stretched.
If your car has two belts, it's recommend replacing both at the same time, because you are saving on labour and time. It's also a good idea to replace or at least check an old serpentine belt before a long road trip.
Twitter and Instagram; @VverteAutoSevcs
Email; vverteautosevcs@gmail.com
Phone; 09137103730
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