DIY Timing Belt Replacement: A General Guide
Steps of a Timing Belt Replacement
What you'll do depends on the specific model you'll be working on, but these are the basics common to all:
- Knowing the specific components you need to remove to gain access to the timing belt.
- Finding all the timing marks to synchronize the camshaft and crankshaft sprockets.
- Setting cylinder number one to Top Dead Center.
- Replacing related hardware.
- Properly threading and applying tension to the belt.
- Tightening bolts to torque specifications to prevent engine performance problems.
When Should the Timing Belt Be Replaced?
- when the belt breaks,
- when a related component fails, or
- when you reach the manufacturer's recommended service interval.
Unfortunately, most belts get replaced when they break because of wear, because of some hardware related failure (bad idler pulley, failed tensioner, oil or water leaks), or because the belt stretched too much and caused some engine performance problems.
Problems You Might Find With Your Timing Belt:
- Retarded ignition timing
- Engine knock or pinging noises
- Lack of engine power
- Poor fuel economy
These symptoms, though, may show up when problems develop in other systems as well. So you can't rely on them to signal problems with the timing belt.
That's why many car manufacturers recommend replacing the belt every 5 years (or 60,000 miles) for older vehicle models (1995 or before); or every 8 years (or 100,000 miles) for modern vehicle models.
You'll Need Your Manual
If you are ready to replace the timing belt in your car, this guide shows you a general procedure to replace a timing belt. You'll know what is necessary to install a new timing belt, the key points you need to pay attention to, and the proper recommendations to get the job done.
However, keep in mind that you'll need the repair manual for your specific vehicle make and model for this project. If you don't have the manual yet, you can buy a relatively inexpensive from Amazon. Haynes manuals come with step-by-step procedures for many maintenance, repair, and troubleshooting jobs. The manual is likely to pay for itself after your first project. So now is the best time to get it. Haynes manual
Answers You'll Find In This Article
- What is a Timing Belt
- When to Replace a Timing Belt
- What Happens When a Timing Belt Breaks
- Does My Car Have a Timing Belt or Chain?
- Timing Belt Tools
- Removing the Timing Belt
- Installing the Timing Belt
- Making the Most of a Timing Belt Replacement Project
I. What Is a Timing Belt?
Toothed timing belts are used in most engines with overhead camshaft (OHC) configurations. They are usually made of neoprene, a synthetic rubber highly resistant to oil contamination and resistant to wear. Nylon and fiberglass are commonly added to give the belt better strength and reduce stretching as much as possible.
The timing belt's job is to keep the crankshaft and camshaft in the same rotating position relative to each other. This is accomplished by aligning marks on the camshaft and crankshaft sprockets during timing belt installation.
It is this cam and crankshaft synchronization that allows the intake and exhaust valves to open and close according to the position of the pistons during their four-stroke cycle.
The belt itself has square teeth that mesh with the sprockets' teeth, allowing the crankshaft to drive the camshaft in synchrony. In addition, the crankshaft may also run the oil and water pumps using the belt.
To prevent upsetting ignition timing as the belt wears and stretches, a spring-loaded tensioner, sometimes hydraulically operated, maintains the correct belt tension.
2. When to Replace a Timing Belt
Unless the timing belt breaks, most car owners forget about the existence of the belt, let alone the need to replace it.
The best time to replace the belt is on your manufacturer's recommended change interval (usually between 50,000 and 100,000 miles), even if it looks in good condition.
You can find the timing belt service schedule in your vehicle repair manual. If you don't have the manual yet, check this guide from the Gates Corporation.
Other than following the service schedule, a timing belt sometimes need to be replaced because of problems with the belt itself or related hardware. For example:
A timing belt may show signs of:
- exposed rubber
- missing tooth
- soften spots
- rounded edges
- oil or water contamination
A belt can reach the end of its service life prematurely because of heat, oil, and other potential contaminants that can reduce its service life.
Related hardware may also cause problems:
- The belt tensioner may fail.
- A sprocket may get damaged.
- A pulley may wear out
Any of these signs indicate the need for a new timing belt.
A timing belt that's been in service for a few years, though, won't necessarily look worn. Belts can look good on the outside, but internally they can be too worn and can tear apart without warning.
Here's a simple test that can help you determine the condition of the belt:
- Press your fingernail against the back of the belt.
- If you can leave the impression of your fingernail on the surface of the belt, it's likely you can wait to replace the belt until the recommended service interval.
- If you can't leave the impression of your fingernail, the belt has hardened and it's better to replace it before it breaks.
And if the belt breaks, it can cause considerable damage. Continue to the next section.
3. What Happens When a Timing Belt Breaks
What happens if your belt breaks during engine operation depends on the type of engine you have.
Engines are classified as interference or non-interference.
This basically means that if you have an interference engine (most imported and some domestic models), the intake and exhaust valves share space with pistons inside the cylinder and combustion chamber as they both move up and down.
When the valves retract or close, the piston is in its highest position within the cylinder. When the valves open, they extend into the combustion chamber when the piston is in its lowest position in the cylinder, thus preventing the collision between the two.
However, if the timing belt breaks, the valves will stop moving. Those valves in the open position will crash against the still moving pistons. Damage to the valves and piston occurs. And you're left with an expensive repair.
On a non-interference engine, a broken timing belt won't destroy the engine, but will cause the engine to shut down, which may put you in danger if the belt happens to break in the middle of the road. And the engine won't run until you replace the timing belt.
4. Does My Car Have a Timing Belt or a Chain?
Some vehicles use a timing chain instead of a belt. If your vehicle has a timing chain, you don't have to worry about replacing it. For the most part, timing chains don't need to be changed unless something makes it necessary.
There's nothing on the outside of the engine that can tell you whether the engine uses a chain or a belt, but usually, a quick search online can help you here. For example, you can search for:
"2005 Chevy Cavalier 2.0L timing belt"
"2005 Chevy Cavalier 2.0L timing chain"
and see what you find.
And of course your vehicle repair manual will have this information. Or you can call your local auto parts store or local dealer.
5. Timing Belt Tools
Before you begin your project, consult your vehicle repair manual for any special tools you may need for the job on your particular model.
For example, you may need a:
- belt tension gauge
- pulley tool handle
- tensioner pulley tool
- tensioner adjuster tool
- crankshaft wrench tool
Some auto parts stores carry some of these tools, and others may be ordered through your local dealer or online.
6. Removing the Timing Belt
Once you've gathered all the necessary tools and have your repair manual on hand, you're ready to remove the timing belt.
- Disconnect the negative battery cable and secure it away from the battery post.
- On some models, you can remove the timing belt cover without removing any other component, but on other models, you will first have to remove one or more accessory belts, hoses, or other components that may prevent you from getting access to the cover. If necessary, remove the cooling fan, alternator, or power steering.
- After clearing the space, remove the cover. Depending on your particular model, the cover will be a piece of sheet metal or plastic.
- After removing the cover, check for any other sensors, wires or accessories that may prevent you from removing the belt.
- Locate the timing marks on the camshaft and crankshaft sprockets. Sometimes, these marks are not too evident. Locate the marks with the help of your repair manual and, if necessary, use a piece of chalk or white-out to make them easier to see.
- Align the timing marks following the procedure described in your particular repair manual. This will set the number 1 cylinder to top dead center (TDC).
- Carefully loosen the adjustment bolt located on the belt tensioner pulley.
- After loosening the belt's tension, slip the belt off the crankshaft sprocket.
- Remove the crankshaft pulley, following the procedure indicated in your vehicle repair manual. And make sure the crankshaft sprocket doesn't move, or you'll lose the timing alignment.
- After removing the crankshaft pulley, remove the timing belt from the vehicle.
7. Installing the Timing Belt
Although every step of the process during a timing belt installation is important, aligning the camshaft and crankshaft is critical.
You should know about and locate all the alignment marks for your particular model, and know how to align them. Every model is different, so make sure you consult your repair manual when installing the timing belt.
Now that you're ready to install the belt:
Purchase a quality brand replacement belt to guarantee durability.
Compare the old belt to the new one in width, length, and tooth configuration.
To start installing the belt, position the belt around the crankshaft sprocket.
Install the crankshaft pulley, following the instructions in your vehicle repair manual.
Double-check that the marks on the crankshaft sprocket or pulley align with the marks on the engine block. If not, carefully rock the pulley until the marks line up.
Double check that the marks on the camshaft sprocket align with the marks on the cylinder head.
Thread the timing belt around the camshaft sprocket as described in your manual.
Apply pressure to the belt by moving the tensioner into the belt. This will help to hold the belt in place. Then, follow the instructions in your repair manual to properly set the belt tension.
Using the proper tension prevents the belt from wearing prematurely (too tight) or vibrating, sliding off the sprockets, or jumping time (too loose).
A quick test to know if the belt has the correct pressure:
Use your thumb and index finger to turn the belt about a quarter of a turn.
If you need to apply reasonable pressure to turn the belt, it has the proper tension.
After the timing belt is in place and the proper tension has been set, reinstall any sensors or brackets you had to remove.
Reinstall the timing belt cover.
Reinstall any accessories you had to remove to access the timing belt cover.
Connect the negative battery cable to the battery.
Start the engine to make sure it operates properly.
The next video shows an adjustment you may need to make to align the timing marks on some models.
Timing Marks Alignment
8. Making the Most of a Timing Belt Replacement Project
Replacing a timing belt can take you 3 or more hours of work in your garage, on average.
However, this will depend on:
- your mechanical skills
- whether you've done this repair job before
- the tools you have on hand for this job
- your particular vehicle make and model
Some models require more tools and time because of the number of accessories you need to remove, and the amount of space you are left with to work around the belt. On some models, you practically need to lift the engine off the bay to work on the belt.
Take into account all these factors, and think about replacing other maintenance items that you have access to only when removing the timing belt. For example for some models, many shops suggest that when you install a new timing belt you replace replacing the water pump and, in some special cases, the oil pump, since you would need to remove the belt to replace these components when they fail.
So, depending on your car model, think not only about getting a timing belt replacement kit, but also a new water pump and, if necessary, an oil pump.
Replacing one or more of these components at the same time will save you money and time in the near future.
This article is accurate and true to the best of the author’s knowledge. Content is for informational or entertainment purposes only and does not substitute for personal counsel or professional advice in business, financial, legal, or technical matters.