Instead of a mileage or time-based replacement, you should look for signs of a failing timing chain, which would necessitate replacement. These signs include:
* Loud ticking or rattling noise from the engine: This is often the first and most prominent symptom. The noise will usually worsen as the engine warms up or under load.
* Engine misfires or rough running: A stretched or damaged chain can cause the timing to be off, leading to misfires.
* Loss of engine power: Similar to misfires, incorrect timing will reduce the engine's ability to produce power.
* Check engine light: A misfire or other related problem will often trigger the check engine light.
* Oil leaks: Wear on the chain guides or tensioner can lead to oil leaks.
Because a broken timing chain can cause catastrophic engine damage (bent valves), it's best to address any of these symptoms *immediately*. A mechanic can inspect the timing chain and its components to determine its condition and whether replacement is necessary. It's a preventative maintenance decision based on the age and condition of the vehicle, not a set mileage interval.
