The timing system of the engine synchronizes the crankshaft and the camshaft. It ensures that the valves open and close at exactly the right time to inject fuel and remove exhaust gases. This precise sequence must work perfectly and at any engine speed. After all, it ultimately determines how the engine runs, the power it delivers, the fuel consumption and emissions of the vehicle.
An increasing number of vehicles are equipped with a chain in the original equipment of the timing drive. Compared to belt drives, higher forces can be transmitted with timing chains. Even though these chain-driven engines are considered to be maintenance-free and designed for the lifetime of the engine even the robust chain drives are subject to age-related, use-dependent wear.
The vibrations and forces occurring in the engine and the use of unsuitable oil or lack of regular maintenance create a large load on the components installed. Since the chain drive components work in concealment, this wear is not always directly noticeable during inspection. Nevertheless, an impending defect is often announced acoustically. The typical “chain rattling” usually indicates an imminent chain drive failure at an early stage.
Chain stretch is also an occurrence that can cause engine problems as well. A chain that has stretched too much can cause a check engine light to illuminate due to the timing of the engine no longer in sync. Along with the check engine light on, there may be an engine misfire, poor acceleration, excessive fuel consumption, and increased emissions.
Most chain driven engines are also interference motors. In an interference engine, this can cause pistons that are still moving due to inertia to hit some of the valves that are in a fully open position if the chain were to break suddenly while the engine was running. If this happens, the pistons can bend or even break the valves. In some cases, an engine might be severely damaged as a result.
When a timing chain needs replaced it is recommended to replace the components associated with the chain as well. This may be chain guides, sprockets, tensioners, and possibly water pumps as well. Considering the effort and labor required to replace a timing chain it’s not worth saving a few dollars to not service them as well.
This video is sponsored by INA, a Schaeffler Brand.
