A toothed belt has a number of advantages over a drive chain. The latter is clearly more expensive. Making a belt is much easier than making a chain. Essentially, a toothed belt is a closed belt made of oil and petrol resistant rubber, reinforced with a nylon cord with teeth vulcanized to it. If you compare a belt with a chain, then the comparison will not be in favor of the latter. The belt is much lighter than the chain, which, of course, cannot but affect the mass of the engine. In addition, a belt-equipped engine is much quieter than its chain-equipped counterpart. And mounted «rubber» outside the engine cover, which affects the time of its installation or replacement. For example, it takes about 25-30 minutes to replace the timing belt of a four-cylinder eight-valve engine with its subsequent installation according to the marks. With a chain, such a trick will not work.
With proper maintenance, the toothed belt runs for a long time. Domestic manufacturers, recall, give a guarantee for a mileage of 60 thousand km, foreign - and even more. Rover managed to push back the timing of belt replacement to 160,000 kilometers.
What is the correct maintenance of the belt drive? At least every 15–30 thousand km, the belt tension should be checked. However, this does not mean that it is only necessary to bend the casing and check if the belt is in place. It is best to inspect it by removing it from the engine. Sometimes it is difficult to notice that one of the teeth is undercut. If this has already happened, then be sure that he will not last long. Therefore, having removed the belt, make a mark on it with chalk, and then examine it tooth by tooth. After installation, it is also necessary to check the position of the guide and tension rollers. All these elements must be in the same plane, otherwise the belt will work skewed, which will significantly reduce its resource.
An important factor for the operation of the belt is the absence of oil on its surface. Whatever the oil and petrol resistant rubber from which the belt is made, it is still not the case when «you can't spoil porridge with butter». This is where oil comes in handy. Therefore, periodically it is necessary to pay attention to the condition of the oil seals of the camshaft and crankshaft. And if you already notice an oil leak, try to fix it as soon as possible. As practice shows, the presence of a belt in oil reduces its resource by half, or even three times.
If this control is ignored, the consequences will not be long in coming. After 40–50 thousand km, by pulling the belt, its tension will weaken and it will start «whip». As a result «heavy» the camshaft does not rotate synchronously with the crankshaft, but lags behind. This «asynchronous» work leads to an even greater weakening of the belt tension. The result is an excessive load on the teeth.
Attention! The breakage of several teeth in a row can lead to the fact that at one point the camshaft will remain stationary, while the crankshaft will rotate. It was at this moment that the open valves of the cylinders «will meet» with pistons. The result is a broken stem or bent valve, broken guide bushings, broken camshaft. There are, however, exceptions when the cliff is almost painless. However, this is only possible on those vehicles whose engines have grooves in the pistons specially for this case. These, for example, include our VAZs, namely cars VAZ-2105 with engine 1300 cm3 and VAZ-2109 with engine 1500 cm3.