Timing belt or timing chain? Your car definitely has one or the other, so let us explain what sets them apart.
Your average car’s internal combustion engine is a precision instrument, even if you’re talking about an old banger. But with so many parts working together, and most of them needing maintenance of some kind, it’s easy to neglect some key components when they’re due for servicing or outright replacement.
Aside from your scheduled oil changes and other fluids, your timing belt or timing chain is critical to the engine’s operation. If that fails, it could be game over for that once-reliable motor. This is because both function to keep the camshaft and crankshaft working together closely
The camshaft is responsible for the opening and closing of intake and exhaust valves in the engine. Should that be mis-timed or completely out of tune, the basic cycle of a four-stroke engine - intake, compression, combustion, exhaust - would stop.
Each of those four steps requires the camshaft(s) to open and close the intake or exhaust valves in perfect synchronicity (a.k.a timing) across all cylinders for an engine to run, letting air (or fuel + air if using port injection) in and exhaust gases out as needed. And making sure that’s always happening is the timing belt, or timing chain.
Chain vs Belt
They both work the same way, essentially. Though, there are 2 main differences, and they’re both fairly obvious: material and location.
Timing chains are the older of the two and is, as the name describes, an actual metal chain much like the ones you’ll find on your bicycle or a motorcycle, connecting the crankshaft to the camshaft.
They are also housed within the block itself and isn’t visible during normal operation, requiring partial engine disassembly to access. But thanks to this alongside the inherent durability of the metal chain material, timing chains are much better insulated from the elements and other outside wear factors. Coupled with it being in constant lubrication from the engine oil, they last much longer than timing belts.
Of course, a manufacturer would often include maintenance notices for timing chain replacements, just in case - usually at 100,000km. However, a lot of high quality timing chains have been known to last the lifetime of the vehicle if properly maintained, and the best thing you could do to ensure timing chain longevity is to always make sure you have clean high quality oil coursing through the engine.
On the other hand, timing belts were first seen in cars from the 1960s and designed to mitigate some of the downsides of the timing chain, namely noise/vibration and, to a much larger extent, cost. The simple fact was that using a rubber belt to keep engine timing in sync was a cheaper way to mass produce an engine.
Automakers would then use different material formulations to make a more durable timing belt, but of course it could never be as strong as a timing chain made of high strength steel. The belt would also need to endure the high temperature, humidity, and the occasional attack from the various chemicals and pollutants that accumulate in the engine bay since they are not insulated within the engine.
As a result, a timing belt can begin to stretch and/or crack over prolonged use, requiring replacement much sooner than your typical timing chain. Thankfully, a timing belt is relatively cheap and, because it’s accessible from the engine bay and usually with little to no disassembly, it’s also much easier to inspect its condition as well as to swap a worn belt for a new one if necessary.
Better Safe Than Sorry
To stay on the safe side, always replace a timing belt according to the manufacturer’s recommendations, or sooner to be even safer, and the same goes for a car fitted with a timing chain. Though the likelihood of a chain failure is significantly less compared to a belt, the likelihood that it could lead to a catastrophic problem is still present.
In 2020, engines are much more complex compared to a mere decade ago. More demands are placed upon them to be smaller, more fuel efficient, more powerful, and to produce fewer emissions.
As a consequence, these factors have forced automakers to phase out timing belts due to the more highly stressed nature of these newer engines. Here, stronger timing chains are called upon as rubber belts are just less dependable and more prone to accelerated wear and failure when the going gets tough.