Symptoms of a Broken Timing Chain

by Paul Novak
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rusty chain image by Leonid Nyshko from

There are two main types of connections used in automobile engines to synchronize the operation of the valve train with the rotation of the crankshaft. Smaller import vehicles tend to use rubber and fiberglass timing belts to make this connection, while larger American automobiles more commonly use metal timing chains. Regardless of the type used, the symptoms of a broken timing chain or belt are similar because they both perform the same function.

Engine failure

A timing chain that has broken completely will no longer connect the crankshaft to the camshaft. This will result in the camshaft no longer opening and closing the valves, and the engine will not run. This is usually noticed as a sudden failure of the engine while in operation as if the engine was suddenly shut off. Attempts to restart a vehicle after the timing chain has broken will be unsuccessful.

Poor running

A broken timing chain can create slack in the connection between the crankshaft and camshaft. This will cause the valves to open and close later than they should, causing reduced combustion chamber pressures and incomplete ignition of the fuel and air mixture. The result is misfiring and rough idling of the engine.

Reduced power

A timing chain that has stretched enough to skip a couple of teeth on the sprocket will not allow the combustion chambers to draw in the proper amount of fuel and air mixture, because the valves will not be opening and closing at the right times. This causes a significant reduction in power and diminishes the responsiveness of the engine to input from the accelerator pedal.


A broken timing chain may move around excessively and contact the timing chain cover, or jump around on the crank and camshaft gears causing rattling and knocking noise to come from the front of the engine. In severe failures on some engine models, a broken timing chain will cause the valves to come into contact with the pistons, resulting in very loud knocking and banging noises, catastrophic engine failure, and destruction of the valves and pistons.

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