A timing belt and a serpentine belt may sound similar, but they have different roles in your engine. A serpentine belt is visible when you lift your hood, and it's responsible for transferring rotational power from the engine to power the alternator, power steering pump, air conditioning and more. A timing belt is deep within the engine and controls the movement of different parts to ensure your engine keeps running.
Both types of belts need to be replaced roughly every 60,000 to 100,000 miles, but replacing a timing belt is much more expensive than replacing a serpentine belt. And if the timing belt fails, your whole engine could be ruined.
What Is a Timing Belt?
A timing belt controls critical moving parts in your engine, including the camshaft, which controls air intake and exhaust, and the crankshaft, which moves the pistons in the engine. With these pieces moving in sync, the engine produces a steady stream of power.
While both a timing belt and a serpentine belt are important parts of your vehicle, the timing belt is critical. If it goes, your whole engine can fail because the parts of a cylinder aren't moving at the right time.
Timing belts are made of rubber or rubber-like material, with reinforcing cords made from Kevlar or other very strong material. Timing belts have "teeth," or indents, cut into the side. These grooves fit into similar grooves on the crankshaft and camshaft. Since timing belts are deep within the engine, you can't see them when you glance under the hood.
What Is a Serpentine Belt?
A serpentine belt is a smooth rubber belt that's easily visible on the surface of your engine. The serpentine belt winds over the water pump, power steering pump, alternator, air conditioning compressor and other car components. When your engine runs, the serpentine belt transfers rotational power from the engine to these components, allowing them to work.
If your serpentine belt goes, it might lower power steering, charging or other systems, but your engine will still generate power.
Repair Costs
Replacing a timing belt is more expensive than replacing a serpentine belt. Here's what you can expect to pay.
Timing belt repair costs
Timing belt replacement costs about $600 to $800, on average. Roughly half of the cost is for materials for the new belt, and the other half is for the labor to install it.
If your timing belt breaks on the road, you're looking at a much more expensive repair. That's because a broken timing belt can damage other engine components. Repairs to the engine can cost $2,000 or more. In fact, sometimes they're not even worth making because they're so expensive.
Serpentine belt repair costs
If your serpentine belt goes, you'll pay about $120 to $150 for a new one. The cost is made up equally of the cost of the new belt and the labor to install it.
Comparing Lifespan and Maintenance
A timing belt and a serpentine belt are both wearing parts that need to be replaced every 60,000 to 100,000 miles. That's a wide range, so it's best to follow your owner's manual to know when to replace your belts and learn to recognize signs that the belts are failing.
Remember, it's important to repair a timing belt before it fails to avoid costly engine repairs.
Signs of a failing timing belt
You should always replace your timing belt at the mileage your manufacturer recommends. If the timing belt fails, it can ruin your engine—so preventive maintenance (i.e., replacement) is essential for timing belts.
However, it's also important to recognize the signs of a failing timing belt in case yours goes sooner than expected. Signs include:
- A ticking noise inside the engine
- Engine misfires
- Trouble starting the car or getting the engine to turn over
- An oil leak
- Smoky exhaust fumes
- Revolutions per minute (RMPs) that are running high or not staying stable
If you notice these signs, see a mechanic immediately. They can look at the timing belt to identify signs of wear or stretching.
Signs of a failing serpentine belt
Like a timing belt, a serpentine belt should be replaced before it goes bad, usually every 60,000 to 100,000 miles. Your owner's manual will have the specifics for your car.
The first sign of a failing serpentine belt is often a whining noise from under the hood. This means that the belt is loose or has slipped. Other signs of a failing serpentine belt include:
- Squealing or chirping from under the hood
- Loss of power, including a stalled engine
- Check engine light
If your serpentine belt fails, you'll notice more obvious signs, like the loss of power to essential components of your vehicle. The signs of a broken serpentine belt include:
- Power steering failure
- Air conditioner failure
- Dead battery or trouble starting the car because the alternator has no power
- Engine overheating due to lack of water pump
Tips for Belt Maintenance
Both timing belts and serpentine belts are wearing parts, so they're not expected to last the whole life of your vehicle. However, there are some maintenance tasks you can perform to reduce the chances of your belts failing unexpectedly.
- Check your belts. When you get your oil changed or engine serviced, ask the mechanic or technician to look at the belts. Note: This is easier with the serpentine belt, which is more visible.
- Check pulleys and tensioners. Pulleys and tensioners help your belts function properly, so ensure that they're in the right positions.
- Follow maintenance recommendations. Replacing the belts before they fail can save you time and money.
Keep Your Belts Turning
Preventive repairs and replacements are essential for your timing belt or serpentine belt. If it's been awhile since your belt was replaced, ask your mechanic when you're due for a new one. If you notice signs of a failing belt—like strange noises from under the hood—don't delay a trip to the mechanic.
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