Some cars have a timing belt that’s hidden out of sight behind the engine’s front cover. You might not think that a belt sounds like a big deal—but the timing belt is a big deal because it can cause catastrophic engine damage if it fails.
It’s helpful to understand how the timing belt works and when it should be replaced. That way, you can avoid potential problems down the road.
What is a Timing Belt?
The timing belt is a toothed belt (located behind the engine’s front cover) that’s used to keep the engine’s crankshaft and camshaft(s) in synch. You’ll find that the belt loops around the crankshaft and camshaft sprockets and also drives the engine’s water pump.
A typical timing belt is made from sturdy rubber (molded polyurethane, neoprene, or urethane). The belt usually has a high-tensile cord of fibers running its length and a facing fabric covering its teeth.
What Does a Timing Belt Do?
Before you can comprehend the role of the timing belt, it helps to have a basic understanding of the internal workings of the engine. Inside the engine, there is a crankshaft and one or more camshafts. The crankshaft is attached to the connecting rod and piston assemblies, whereas the intake and exhaust valves are operated by the camshaft(s).
The crankshaft and camshaft(s) must be kept in sync (“in time”) so that the pistons are at the correct point of travel when the valves open and close. Depending on the engine design, either a timing belt or timing chain is used to connect the crankshaft to the camshaft(s), thereby keeping the engine in time.
A tensioner pulley and one or more idler pulleys are used to secure and keep tension on the timing belt. It’s also important to note that the timing belt drives the engine’s water pump.
Example Timing Belt Diagram
Below, you’ll find a timing belt diagram for a 2005 Honda Civic 1.7L. Keep in mind that this diagram is only an example. You can find the timing belt diagram for your vehicle by consulting a repair manual or an online repair database.
Timing Belt vs. Timing Chain
The crankshaft and camshaft(s) of an internal combustion engine must always be kept in synch. Depending on the engine’s design, this task is almost always accomplished with either a timing belt or a timing chain (some engines use timing gears, but that setup is rare and typically used in heavy-duty trucks).
Most engines built within the last ten years or so have a timing chain instead of a timing belt. But there are still many vehicles on the road with a timing belt under the hood.
Timing Belt
As was mentioned, a timing belt is a toothed rubber belt that wraps around the crankshaft pulley, water pump pulley, and camshaft pulley(s).
The timing belt is considered a wear item because it’s made of rubber that can eventually stretch or break. As such, the timing belt requires periodic replacement. The belt should be replaced according to the vehicle manufacturer’s maintenance schedule.
Watch this video to get an idea of how timing belts work:
Timing Chain
On the other hand, a timing chain is a metal chain made up of a collection of links. The timing chain wraps around the crankshaft sprocket and camshaft sprocket(s). Engines with a timing chain might use the chain to drive the water pump, or (more commonly) the pump is driven by the serpentine belt.
Timing chains are supposed to last the life of the vehicle (though that doesn’t always happen). Because of this, timing chains do not have a recommended replacement interval.
What Causes a Timing Belt to Break?
A timing belt can stretch or break for several reasons. Here are the most common:
Wear Due to Time and Miles
Timing belts eventually wear out, which is why vehicle manufacturers recommend periodic replacement. If you don’t replace your car’s belt on time, it could stretch or break, potentially resulting in extensive internal engine damage.
Failed Tensioner, Idler Pulley, or Water Pump
If the timing belt tensioner or idler pulley fails, the timing belt can break as a result. The timing belt might also break if the water pump’s bearings fail.
Fluid Leaks
Coolant from a leaking water pump or oil from a failed engine seal can contaminate the belt and cause it to fail prematurely.
Seized Engine
A seized engine can create tension that causes the timing belt to snap.
What are the Symptoms of a Bad Timing Belt?
A broken or stretched timing belt is bad news because it can lead to catastrophic internal engine damage. Most engines have what’s referred to as an interference design, which means the valves usually contact the pistons when the timing belt breaks.
If the timing belt fails, you might notice one or more of the following symptoms:
Note: Other problems can mimic a failed timing belt. You (or your mechanic) should perform a thorough diagnosis before conducting any repairs.
Engine Doesn’t Start
Your car won’t start if the timing belt breaks. Typically, the engine will crank faster than normal but refuse to fire up.
Engine Runs Rough and Misfires
A stretched or jumped timing belt will typically result in the valves not opening and closing at the right time. As a result, the engine will experience a loss of compression, causing it to run rough and misfire.
Illuminated Check Engine Light
Your car’s engine computer management system looks for anything that could lead to an increase in tailpipe emissions, including a misfire and other problems caused by a stretched timing belt. If the system determines there’s an issue, it turns on the check engine light and stores a corresponding diagnostic trouble code (DTC) in its memory.
How to Check a Timing Belt
Unfortunately, there isn’t an easy way to tell whether a timing belt is worn out and needs to be replaced. Even if you peel back the timing belt cover to perform a visual inspection, it’s hard to tell whether the belt is worn out. That’s why it’s important to follow the manufacturer’s maintenance schedule regarding timing belt replacement.
But if the timing belt is broken, you can often confirm this by removing the upper timing belt cover to perform a visual inspection. Some vehicles also have a dedicated inspection cover that you can remove to inspect the timing belt.
If you can’t get a peek at the belt, you can perform a compression test on the engine. Low compression on all of the engine’s cylinders often indicates a failed timing belt, as the video below demonstrates.
Another timing belt test method involves using an oscilloscope (if you’re lucky enough to have one), as outlined in the video below.
How to Replace a Bad Timing Belt on a 2005 Honda Civic 1.7L
Replacing a timing belt is a big job that can result in significant engine damage if performed incorrectly. So, if you have any doubts about your automotive repair abilities, it’s best to leave the job to a qualified professional.
For an idea of what replacing a timing belt typically involves, here are some instructions outlining the job on a 2005 Honda Civic.
Tools and Equipment Needed
You’ll need the following tools when performing a timing belt replacement on a 2005 Honda Civic 1.7L.
- Breaker bar
- Honda crankshaft pulley tool
- Pushpin removal tool (recommended)
- Jack and jack stands
- Ratchet and socket set
- Repair manual or access to a repair database
- Safety glasses
- Screwdrivers
- Torque wrench
- Wheel chocks
- Wrench set
2005 Honda Civic 1.7L Timing Belt Replacement Instructions
One thing to keep in mind is that most professionals also replace the water pump, along with the camshaft and crankshaft seals, as a preventative measure when replacing the timing belt. But in this article, we’re just going to focus on replacing the belt and automatic tensioner.
Note: The following are general guidelines for educational and entertainment purposes only. Consult your vehicle’s factory information for specific repair instructions and recommended safety procedures.
Timing Belt Removal
- Ensure you have the anti-theft code for the car’s radio. The radio will be locked out once the battery is disconnected.
- Put on your safety glasses.
- Disconnect the negative battery cable.
- Use a breaker bar to loosen the left front wheel’s lug nuts. Do not remove the nuts completely at this time.
- Safely raise and support the vehicle using a jack and jack stands. Set the parking brake and chock the rear wheels.
- Remove the lug nuts by hand. Then remove the left front wheel and tire assembly.
- Use a pushpin removal tool or small screwdriver to remove the pushpins from the splash shield. Remove the splash shield from the vehicle.
- Remove the power steering pump adjustment plate mounting bolt, locknut, and mounting bolt.
- Remove the power steering pump and set it aside and out of the way without removing the lines.
- Disconnect the electrical connector and cable from the alternator.
- Loosen the alternator adjustment plate mounting bolt, locknut, and mounting bolt.
- Remove the alternator belt and the alternator.
- Remove the ignition coil cover. Disconnect the electrical connectors from the ignition coils.
- Remove the ignition coil retaining nuts and remove the ignition coils.
- Remove the fasteners securing the throttle cable clamps and harness holder. Set the cable and holder aside and out of the way.
- Remove the fasteners securing the valve cover and remove the cover.
- Support the engine using a jack and block of wood.
- Remove the three nuts from the upper motor mount bracket and remove the bracket.
- Remove the grommet from the upper timing belt cover and disconnect the camshaft position sensor’s electrical connector.
- Remove the fasteners securing the upper belt timing cover and remove the cover.
- Remove the bolts securing the side motor mount bracket and remove the bracket.
- Hold the crankshaft pulley with the special Honda crankshaft pulley holding tool. Then, use a breaker bar and socket to remove the crankshaft pulley bolt.
- Use the crankshaft pulley holding tool to turn the crankshaft pulley counterclockwise until its top dead center (TDC) mark lines up with the pointers on the timing belt cover. The “UP” marks on the camshaft pulley must also be at the top. In addition, the TDC marks on the camshaft pulley must align with the top end of the cylinder head.
- Wiggle the harmonic balancer off while making sure not to lose the alignment key.
- Disconnect the crankshaft position sensor’s electrical connector and move the wiring harness out of the way.
- Remove the fasteners securing the lower timing belt cover and remove the cover.
- Remove the crankshaft positions sensor’s retaining fastener and remove the sensor.
- Loosen the timing belt tensioner to remove the timing belt.
- Remove the timing belt tensioner retaining fastener and the tensioner.
Timing Belt Installation
- Compare the new timing belt to the old timing belt to ensure both are the same design.
- Mount the new timing belt tensioner in place and install the retaining fastener by hand. Do not tighten down the fastener completely at this time.
- Check the timing marks. Make sure the TDC mark on the crankshaft pulley aligns with the pointer on the oil pump. The “UP” marks on the camshaft pulley must also be at the top. In addition, the TDC marks on the camshaft pulley must align with the top end of the cylinder head.
- Install the timing belt in a counterclockwise sequence by routing it over the crankshaft pulley, then the tensioner pulley, water pump pulley, and finally the camshaft pulley.
- Secure the new timing belt tensioner and use a torque wrench to tighten the retaining fastener down to the vehicle manufacturer’s specifications.
- Double-check that all of your timing marks still line up. If the marks are off even slightly, the engine can be damaged upon startup.
- Reinstall the crankshaft bolt. Then use a breaker bar to turn the engine over two revolutions. Afterward, make sure that the timing marks are still aligned.
- Remove the pin from the new timing belt tensioner.
- Turn the engine over two more revolutions and check that the timing marks are still aligned. Remove the crankshaft pulley bolt from the pulley.
- Reinstall the crankshaft positions sensor and use a torque wrench to tighten the retaining fastener down to the vehicle manufacturer’s specifications.
- Reinstall the lower timing belt cover and use a torque wrench to tighten the retaining fasteners down to the vehicle manufacturer’s specifications.
- Reinstall the harmonic balancer and alignment key.
- Hold the crankshaft pulley with the special Honda crankshaft pulley holding tool. Then, use a torque wrench to tighten the crankshaft pulley bolt down to the vehicle manufacturer’s specifications.
- Reinstall the side motor mount bracket and use a torque wrench to tighten the retaining fasteners down to the vehicle manufacturer’s specifications.
- Reinstall the upper timing belt cover and use a torque wrench to tighten the retaining fasteners down to the vehicle manufacturer’s specifications.
- Reconnect the camshaft position sensor and reinstall its grommet.
- Reinstall the upper motor mount bracket and use a torque wrench to tighten the retaining fasteners down to the vehicle manufacturer’s specifications.
- Remove the jack from underneath the engine.
- Reinstall the valve cover and use a torque wrench to tighten the retaining fasteners down to the vehicle manufacturer’s specifications.
- Reinstall the fasteners securing the throttle cable clamps and harness holder and use a torque wrench to tighten the retaining fasteners down to the vehicle manufacturer’s specifications.
- Reinstall the ignition coils and use a torque wrench to tighten the retaining fasteners down to the vehicle manufacturer’s specifications. Reinstall the ignition coil cover.
- Reinstall the alternator and alternator belt. Adjust the belt tension, then use a torque wrench to tighten the retaining fasteners down to the vehicle manufacturer’s specifications.
- Reinstall the power steering pump and power steering pump belt. Adjust the belt tension, then use a torque wrench to tighten the retaining fasteners down to the vehicle manufacturer’s specifications.
- Reinstall the splash shield.
- Reinstall the wheel/tire assembly on the lug nuts.
- Tighten the lug nuts until they’re snug using a ratchet and socket.
- Safely remove the jack stands and lower the vehicle.
- Use a torque wrench to tighten the lug nuts to the manufacturer’s specification.
- Reconnect the negative battery cable.
- Enter the anti-theft code into the radio.
Check out the videos below for a visual representation of what the job involves.
When Do I Replace a Timing Belt?
You should always replace your car’s timing belt per the vehicle manufacturer’s service schedule. If you postpone replacement, the belt could break, potentially causing extensive (and costly) engine damage. You can find your car’s service schedule in the owner’s manual or supplemental service booklet.
Can I Still Drive My Car with a Bad Timing Belt?
Absolutely not. In many cases, a bad timing belt will prevent the engine from running altogether. But if the vehicle still runs, continuing to drive with a bad timing belt can damage the engine and other costly components.
How Much Does a Timing Belt Replacement Cost?
You can typically expect to pay between $1000 and $2500 to have a professional replace your car’s timing belt. Of course, the exact cost of the repair will depend on various factors, such as the type of vehicle you have and the repair shop you choose.
If you have the tools and the know-how, you can save money by doing the job yourself with a replacement timing belt from CarParts.com.
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Any information provided on this Website is for informational purposes only and is not intended to replace consultation with a professional mechanic. The accuracy and timeliness of the information may change from the time of publication.
I’m a mechanic and I found the article on timing belts to be truthful and accurate. I believe that if people use the information provided in it they will save a lot of engines from bent valves and therefore huge repair costs replacing them versus the relativley minor cost of replacing the timing belt at regular intervals. By the way I am a honest mechanic and have quit more than one shop that wasn’t and I am truly sorry that there are people out there turning wrenches who are dishonest and giving my profession a bad name and violating the trust our customers place in us.
Thank you for the feedback, Daniel! We agree that if more people knew when to replace their car’s timing belt, that knowledge would prevent a lot of headaches!
Thank you Mia Bevacqua, for an excellent, detailed and informative article on Timing Belts.
I know that I never want to attempt that repair myself.
Why would Honda, and other car makers, use the Timing Belt for the water pump? That doesn’t seem logical. It just adds more unnecessary stress to belt. A serpentine belt is cheaper and easier to replace and won’t damage the engine if it breaks. It’s also in plain sight for easy inspection.