Timing chain should last life of engine

By: Jim Kerr Posted: 3:00 AM CDT Friday, Oct. 2, 2015

Question: Recently I read about a truck that needed a possible timing chain replacement. I am a little perplexed by this as I thought timing chains lasted the life of the engine. Do timing chains actually have to be replaced, and if so at what interval?

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Hey there, time traveller!
This article was published 02/10/2015 (3978 days ago), so information in it may no longer be current.

Answer: Any moving part in an engine will eventually wear, and this includes timing chains. There are two types of chains commonly used in automotive engines. The link type, which consists of many small links riveted together in a flexible endless chain, used to be most common. Many manufacturers now use roller chains, similar to a bicycle chain. Many roller chains use single width rollers but some use two rollers side by side, and these are called a double roller chain.

Back in the 1970s, we could expect a link type chain to last about 160,000 kilometres before it would become worn enough to require replacement. Stop-and-go driving or sudden acceleration, dirty oil and high valve spring pressures (typically found in performance vehicles) caused more wear and required chain replacement sooner.

Roller chain life expectancy also depends on load, oil quality and chain size. I have seen chains wear in as little as 30,000 km but most could easily go for the life of the engine. The good news is a timing chain almost never fails — it just wears and becomes stretched. Roller chains use a chain tensioner to keep the chain from slapping around, but if the chain becomes too worn the tensioner can’t control the movement and you can hear a rattling sound from inside the engine as it idles. You also may notice less low r.p.m. power and lower fuel economy, but high-speed power will actually improve.

Unlike timing belts, which have recommended mileage change intervals, there are no recommendations for changing timing chains. If you hear a rattling or knocking sound from your engine, it may be caused by a worn timing chain and the mechanic will recommend it be changed after diagnosing it is the chain causing the noise. The chain tensioner and guides are usually changed at the same time. Keep clean oil in your engine and the chain should last the life of the engine.

james.kerr@sasktel.com