Ask the Mechanic: When do I change my engine timing chain?

What you need to know:

This noise is increasing and my engine has started to lose power, has unstable idling and displays a check engine light

Hello Paul,

I drive a Toyota CAMRY 2003 with a 2AZ-FE engine. Recently, my engine started making a rattling noise, especially in the morning. This noise is increasing and my engine has started to lose power, has unstable idling and displays a check engine light. My service bay technician suggests I replace the timing chain to avoid engine damage. But I thought only the timing belts need replacement. I am seeking your advice.


Hello Kakande, timing chains and timing belts synchronise the opening and closing of valves in the cylinder head while moving the pistons up and down in the combustion chamber. A timing chain or timing belt failure can lead to catastrophic and costly damage of engine valves and pistons.

A timing chain comprises a series of links such as a bicycle chain and runs inside the engine because it needs to be lubricated by engine oil. Ordinarily, you do not need to replace the timing chain at 100,000kms (60,000 miles) the way you replace the timing belt. However, the longer the timing chain is subject to wear and tear, it can have a reduced lifespan due to poor lubrication. Your Toyota 2AZ-FE engine is depicting some symptoms of timing chain failure, which include the following:

Engine misfire due to the stretching of the timing chain and skipping of a tooth on the camshaft or crankshaft gear. This will affect the timing of air intake and compression of the engine to cause poor engine performance and erratic idling or misfiring. Metal shavings are another sign of timing chain failure. These are small metallic pieces from the worn out timing chain that may be visible in the oil from the engine sump when drained during oil service. The metal shavings can also be a result of damaged cylinder head valves or piston rings due to poor lubrication.

A normal engine should have a smooth sound. When the timing chain is loose or damaged, the resultant vibration will cause a rattling sound as the engine runs, especially at cold starts. This should call for immediate attention as it may be a final stage before the chain breaks and causes catastrophic damage to your engine.

A timing chain replacement job takes about six to eight hours. It requires a knowledgeable and experienced mechanic who will use a genuine quality timing chain replacement kit and the manufacturer guidelines and reference points (timing marks) to do the job. The result will be experiencing low revolution per minute engine power and improved fuel economy of your Toyota. You can help to prolong your engine timing chain lifespan by using quality engine oils which meet manufacturer recommended specifications as well as genuine OEM oil filters.

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