If you’re like me and often forget automotive parts, then timing belts and serpentine belts are easy to mix up. They’re both belts, but they really couldn’t be more different.
They differ in their location and building material, and they serve a vastly different purpose in your vehicle’s engine. Each part has a different maintenance interval you should consider.
is a serpentine belt the same as a timing belt?
Don’t confuse a serpentine belt with a timing belt. A serpentine belt and timing belt have two very different roles in your vehicle.
A timing belt is found within the engine and keeps the crankshaft and camshaft “in-time”. When they are in sync, the engine intake and exhaust valves open and close with the pistons so the engine runs smoothly.
A serpentine belt is what connects the engine crankshaft, on the outside, to all of the engine accessories, so they operate smoothly and efficiently.
When you look at the belts, it is also easy to see the difference in grooves. A timing belt has horizontal “teeth” designed to fit into the cogwheels of the crankshaft and camshaft so they stay in sync. A serpentine belt has a triangular V-shaped groove that runs up and down vertically along the belt instead.
In time, belts will need to be replaced (around the same time). You can always ask your mechanic or read your owner’s manual for guidelines.
What are Drive Belts? Serpentine Belt vs. Timing Belt
Most new gasoline engines have 2 drive belts: serpentine belt and timing belt.
Timing Belt:
The timing belt moves and operates your engine’s valves as a part of the cycle of the vehicle’s pistons, while allowing the crankshaft to turn the camshaft. To put it simply and in a way that would make a mechanic cringe, the crankshaft and camshaft are the fundamental aspects of your vehicle’s engine.
The crankshaft and camshaft work together to ensure that your engine properly executes the intake, compression, power, and exhaust strokes to run smoothly.
- Location: You can find the timing belt inside of the engine.
- Function: The timing belt is the belt that controls the camshafts in your engine moving at the same time as the crankshaft opening and closing valves at the right time so that the engine runs smoothly. The timing belt has “teeth” that turns the camshaft in time with the crankshaft.
- Appearance: A timing belt looks like a serpentine belt in that it has horizontal “teeth” made to fit the crankshaft and camshaft.
Serpentine Belt:
The serpentine belt drives various engine parts, including your alternator, power steering pump, air conditioner, etc.
Simply put, your serpentine belt powers many of your car’s functionally necessary and quality-of-life features (for example, your alternator charges your battery and other infotainment systems).
- Location: The serpentine belt resides outside the engine, easily visible when you open the hood.
- Function: Serpentine have many jobs such as, powering the alternator and steering pump, and your ac. In some vehicles serpentine belts also can drive water pumps.
- Appearance: A serpentine has multiple V-shaped grooves that appear vertically along the length of the belt.
Serpentine Belt Vs Timing Belt: When should you Replace?
The serpentine belt in your vehicle is designed to be long-lasting. Under ideal conditions, the serpentine belt in your vehicle should last approximately 60,000 – 100,000 miles. It is also important to have the belt replaced as part of your vehicle’s regular maintenance, even if the belt looks to be in good shape.
Serpentine belts are generally going to cost between $100-250 to replace, depending on vehicle make and model – the price of replacing a serpentine belt is much easier to stomach than a timing belt.
Timing belts will have different replacement protocols based on vehicle, so refer to your owner’s manual, but generally speaking, timing belts will last anywhere from 60,000-100,000 miles.
Average pricing to replace a timing belt is generally between $400-1,000 dollars, depending on the type of car (some are much more difficult to replace than others).
To be cost effective, timing belts should be replaced well before they break – because often times when a timing belt breaks, other pieces of machinery may be damage, and the cost of replacing a damaged belt could be twice as much.
Symptoms of Bad timing belt vs serpentine belt
Symptoms of a Worn Timing Belt:
Signs that you should watch for your timing belt that is worn and should be replaced:
- A ticking noise coming from the engine
- The engine will not turn over.
- The engine hesitates between 2000 – 4000 RPM
- The engine misfires.
- More smoke and fumes than normal
- Oil is leaking from the front of the engine
Symptoms of a Worn Serpentine Belt:
You should be familiar with the following six symptoms that may indicate that a serpentine belt is starting to failed and may need to be replaced:
- Squeaking, squealing or chirping noises from under the hood of the car.
- The check engine light or battery light is on the dashboard.
- The A/C does not work.
- The power steering does not work.
- The engine temperature is running high or overheating.
- A burnt rubber smell.
If you look at the serpentine belt when the car is turned off, you can see some signs of worn:
- Cracks, splits or fraying
- Signs of glazing on the sides of the belt.
- There is separating layers or missing chunks/grooves when you twist the belt.
Differences Between Serpentine Belts and Timing Belts
As we previously mentioned, serpentine belts and timing belts serve different functions. A serpentine belt turns motor-driven components and systems while a timing belt vocationally synchronizes the camshaft with the crankshaft.
Another difference in serpentine belts versus timing belts is based on how they are made. Serpentine belts are typically made from rubber or some polymer-based material that are fairly soft, somewhat elastic.
Timing belts are definitely made of rubber as well, but they are made with fiberglass reinforcement. With the reinforcement of fiberglass, timing belts are inherently stronger than serpentine belts.
While every vehicle will have one or more serpentine belts, they may or may not have a timing belt. Some vehicles will have a timing chain instead of a timing belt. Timing chains do the same job as a timing belt and are made of metal links as opposed to solid and looped pieces of material.
| Difference | Serpentine Belts | Timing Belts |
| Location | Outside engine | Inside engine |
| Functionality | Runs power accessories bolted to the engine | Turns the camshaft(s) which open and close the valves |
| Length | Not more than 0.5 inches of deflection when twisted in the middle | Short diameter |
| Stretch Tension | Not more than 0.5 inches deflection when twisted in the middle | 10% to 30% slackness |
| Groove Design | Horizontal “teeth” | V-shaped grooves |
| Lifespan | 50,000 to 60,000 miles | 60,000 to 100,000 miles |
| Cost of Purchase | $25 to $75 | $20 to $100 |
| Replacement Cost | $100 to $250 | $400 to $1000 |
In the end, there is no “timing belt vs. serpentine belt” comparison there – they can work together, but are two different components serving their own unique purpose. Your drive belts are vital to your car’s longevity – if you don’t have them, you won’t be going anywhere quickly; or at all, for that matter.