How Timing Belt Replacement Works

Timing belt and camshaft wheels
Image Gallery: Engines The timing belt on this engine converts linear energy from the pistons into rotational energy, or torque. See more pictures of car engines.

The buzzer sounds off; it's halftime. Your band takes to the field. Before you know it, though, the trumpets play off-beat, the cymbals slam into each other and the saxophone player simply walks off the field. This, although exaggerated, is what could happen if the drum major, the keeper of tempo, went missing. And in the world of automotive maintenance, visualizing this scenario can help illustrate the timing belt's role and what can go wrong without routine replacement.

Think of the synthetic rubber timing belt, which is reinforced with fiber cords, as the drum major of car maintenance -- meaning it keeps everything in the engine in sync. When the engine is on, it's in constant, timed motion, thanks to the belt, the connection between the crankshaft and camshaft.


So why is this important? The crankshaft converts linear energy from the pistons, which move up and down, into rotational energy that eventually turns the wheels. The camshaft opens and closes the engine's valves to allow air and gas in and out of the engine. The timing belt links the two in harmony. Without it, the pistons and valves would collide.

Obviously, this is bad news for vehicle maintenance as this internal collision can cause destruction fair amount of engine damage. Therefore, it's important to stay ahead of your belt's lifespan -- traditionally replacing it every four years or 60,000 miles (96,561 kilometers) or, in newer vehicles, every 100,000 miles (160,934 kilometers). Be sure to check your vehicle's maintenance manual to see what your car or truck's manufacturer suggests.

So we've all accepted the timing belt's importance, but that doesn't mean you have to spend your days worrying that your belt will force you to pay a large maintenance bill. Instead, you can act as the band director and keep that timing belt in check by watching its wear and arming yourself with the knowledge to replace it. Read on to learn about the wear of your belt, typical tools needed in a repair and how to replace it.


Tools Needed for a Timing Belt Replacement

Timing chain
Some cars use timing chains instead of belts. They're rising in popularity due to their durability -- they often last for the life of the car.

You may not even think twice about your timing belt until it nears replacement time, but don't be lulled into a false sense of security because you haven't hit 60,000 or 100,000 miles (96,561 or 160,934 kilometers) yet on your timing belt. If you happen to be working on your engine and can see the belt, take a look for cracks, shredding or excessive slack.

Furthermore, keep in mind that your timing belt will attain natural wear and tear from the engine environment -- a toasty world that can get up to more than 500 degrees Fahrenheit (260 degrees Celsius). If there are any additional outside factors to the belt's wear, you may need to pick up the pace on vehicle maintenance of your belt. Examples of other factors affecting your auto maintenance schedule include:


  • Oil leaks from surrounding seals that could corrode the belt
  • Living in a dry climate where belts become worn and brittle rapidly
  • Infrequent driving, which causes the belt to become a set shape

Considering these factors and routine car maintenance, chances are you'll need to replace your belt during your ownership of your vehicle. And when that time comes, there are certain tools needed for a timing belt replacement. If you're accustomed to doing your own repair work, you'll likely have most of the tools you need. These include:

  • Socket set
  • Torque wrench
  • Combination wrenches
  • Screwdrivers
  • Drain pan
  • Antifreeze
  • Jack and jack stands

In addition to these tools, you will also need some materials specific to timing belt replacement, such as a new timing belt, timing light, timing belt cover gasket set, belt tension gauge, and bolts or pins to hold the camshaft position during your work. Depending on your vehicle's make and model, you may also need a harmonic balancer puller or three-jaw gear puller to remove the crankshaft pulley if it doesn't just slide off.

And, as with most auto maintenance procedures, one size doesn't fit all. Procedures, tools and belt type needed for timing belt replacement vary depending on vehicle make and model. Therefore, perhaps the most valuable tool of all during a belt replacement is a technical manual from a reputable automotive maintenance publisher, such as Chilton or Bentley Publishers [source: Trottier].

Now that you have your tools lined up and service manual handy, let's take a look at how to remove your old timing belt.


Removing Old Timing Belts

Now, right when you're ready to jump into your car maintenance project, you might become wary of your ability to accomplish this task. However, if you have a moderate knowledge of engines, you will most likely be able to tackle a timing belt replacement [source: Trottier].

In general, a car enthusiast who is not a trained professional should allocate about eight hours to complete this vehicle maintenance procedure [source: Trottier]. The first thing you'll need to do is to remove the old timing belt. Although the procedure will vary based upon the technical manual you're using, in general you should:


  1. Refer to your manual for all proper safety procedures.
  2. Engage the emergency brake.
  3. Jack up the car and support it on jack stands.
  4. Disconnect the negative terminal of the battery for your safety.
  5. Make sure the transmission is in neutral.
  6. Remove all spark plugs.
  7. Remove any plastic shields from underneath the engine.
  8. Drain coolant.
  9. Remove cooling fan and any plastic fan coverings from the front of the engine (usually reverse-threaded, so turn right to loosen).
  10. Disconnect all cooling hoses from engine and label for easy reassembly.
  11. Remove the radiator from the car.
  12. Remove the engine drive belts.
  13. Remove the cap and rotor.
  14. Remove the water pump pulley.
  15. Remove the bolts holding the upper timing belt cover.
  16. Place a socket on the center of the crankshaft pulley. Rotate engine to top dead center (TDC), which means that the first piston in an inline engine is at the top. There's a mark showing TDC on the pulley and the engine.
  17. Loosen the crankshaft pulley bolts. Remove the crankshaft pulley and vibration damper.
  18. Remove the lower timing belt cover.
  19. Mark the location of the main tensioner bolt.
  20. Remove the bolt that holds the tensioner and timing belt cover.
  21. Remove the main adjustment bolt for the tensioner.
  22. Remove the freed tensioner and tensioner spring.
  23. Once the tensioner is off, the belt comes off.

Once you reach this point, you're halfway there. Next up is installing that new timing belt. Continue to the next section to learn what steps to take, as well as the significance of setting tension and lining up your timing marks.


Attaching New Timing Belts

If you're replacing your belt as part of routine vehicle maintenance, then chances are your old belt -- the one you've successfully removed -- kept your engine in time for several years. To do that belt justice and keep your vehicle going strong, people embarking on their own auto maintenance need to take care when attaching new timing belts.

In fact, if Dan Trottier, an automotive technician with Bob's Auto Service Inc. in Saco, Maine, has any advice for timing belt replacement it's to take your time. He says, "Just take your time and you can do it. Don't feel you have to move quickly. Move at your own pace."


Although your technical manual will provide instructions for your car maintenance needs, the basic steps of attaching a belt during this automotive maintenance procedure are to:

  1. Again, make sure the engine is set to top dead center, which will make confirmation of the timing marks easier.
  2. Install a new timing belt and tensioner, making sure to properly align the timing marks as you do so.
  3. Adjust the tension of the new belt.
  4. Confirm all timing marks are lined up.
  5. Put everything back together, following the reverse of the steps in the previous section.

From these steps, the most important ones and those that deserve further discussion are the adjusting of tension and lining up of the timing marks. Just like a bandage that can cut off circulation if it's too tight or not provide enough protection if it's too loose, there's a middle road to take with tension. A belt that is on too tight will not last as long; a belt that is on too loose may skip or jump and fail to keep proper time. This makes your car less efficient and creates the possibility that your pistons and valves will collide. Always refer to your technical manual for exact tension specifications.

Once you have the tension right, you need to confirm all your timing marks are lined up. Lining up your timing marks is similar to setting your watch. If you don't set your watch right, you may be late or early. If you don't set your timing belt correctly, being late or early means your engine won't run efficiently and you run the risk of damaging your engine. Your automobile will have specific timing marks to set. Pay attention to your technical manual when confirming your marks are lined up. Then, proceed with reassembly.

Once you have everything under your hood back together, your new belt is set for its role as drum major of your car. You can take to the field for your halftime show -- or the open highway -- knowing you've enhanced your chances that all the players in your engine will remain on tempo.


Lots More Information

Related HowStuffWorks Articles


  • Carley, Larry. "Timing Chains & Gears." Engine Builder. Oct. 1, 2007. (Oct. 28, 2009)
  • Carley, Larry. "Web Exclusive: Gearing Up for Timing Belt and Chain Work." Tomorrow's Technician. March 27, 2009. (Nov. 1, 2009) web_exclusive_gearing_up_for_timing_belt_and_chain_work.aspx
  • Carley, Larry. "What Goes Wrong With Cars and When." AA1Car Auto Diagnosis Repair Help. 2009. (Oct. 27, 2009)
  • Carollo, John. "Timing Chain Selection: And a look at 'new' and 'how to.'" Engine Builder. June 1, 2006. (Oct. 28, 2009) timing_chain_selection_and_a_look_at_new_and_how_to.aspx
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  • Goss, Pat. "Timing Belt Trivia." MotorWeek Goss' Garage. Season 27. (Oct. 26, 2009)
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  • Juran, Kim. "Replacing a Timing Belt: Saturday Mechanic." Popular Mechanics. March 2007. (Oct. 26, 2009)
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  • Trottier, Dan. Technician With ASE Certification at Bob's Auto Service Inc. in Saco, Maine. Personal correspondence. Nov. 1-3, 2009.
  • Trottier, Dan. Technician With ASE Certification at Bob's Auto Service Inc. in Saco, Maine. Personal Interview. Nov. 2, 2009.