![]() But if the timing belt breaks, piston and valve can meet, resulting in expensive damage that, in the worst-case scenario, may require a new engine. Of course, by the time the piston gets to the top, the valve’s already vacated the space. When the valves open, they move so far down they’re within the piston’s travel area, which allows in more air for more power. On most vehicles it just means you’re walking, but a few older and collectible models, including some performance engines from the 1990s and early 2000s, had an “interference” design. The valves won’t open and close, and the engine won’t run. If the belt breaks, there’s no connection between the crankshaft and camshaft. Timing belts are replaced proactively because they can’t be easily examined for wear. A timing chain, shown under a clear plastic cover for demonstration Photo by Audi Check the owner’s manual for the scheduled maintenance to see if a timing belt is listed (it’s separate from “drive belts,” which are the visible ones). The rubber belt you see under the hood is the serpentine belt, which runs such components as the alternator and air conditioning compressor. You can’t tell which you have by looking, as it’s hidden. But many older vehicles still have them, and may now be near their recommended replacement, which is usually around 150,000 to 175,000 kilometres. Thanks to the availability of more lightweight materials, most auto manufacturers are switching back to chains, which don’t require maintenance. Each one has to turn in harmony with the crankshaft’s revolutions, rotating at half the crankshaft’s speed. Depending on the engine, there will be one, two, or four camshafts. The intake and exhaust valves are activated by the camshaft, which has lobes that push them down to open and then let off so they spring back to close. An “exploded engine” cutaway shows the timing chain at the front Photo by BMW If they don’t, the engine won’t run properly, and that’s where the timing chain/belt comes in. The valves must open and close at precisely the right time. ![]() This entire operation happens hundreds of times per minute. ![]() It’s attached to the crankshaft and this action turns it the crankshaft’s spinning motion is then transferred to turn the vehicle’s wheels.įinally, the exhaust valve opens, the piston moves up to push out the exhaust gases, and then the cycle starts all over again. The spark plug fires and ignites the fuel, and that energy pushes the piston back down. The valve closes, and the piston moves up to compress the air/fuel mixture. This advertisement has not loaded yet, but your article continues below. ![]()
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