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Your Crankshaft pulley worn out? » Read more about common malfunctions • Repair • Replacement manual
Control and propulsion with the crankshaft pulley
The crankshaft pulley is a disc flange that is mounted on the crankshaft and used to drive the various ancillary components in an engine. It is typically very durable, but can easily be replaced in case of damage.
Crankshaft pulley operating principle
The crankshaft pulley can be shaped as a pure drive pulley or as a control pulley. As a drive pulley, it is a pulley featuring a circumferential V-groove, a flat belt pulley or a ribbed belt pulley. The version with circumferential V-groove is designed for the use with V-belts. This design is well-proven, but increasingly being replaced by flat belts or ribbed belts. As a control pulley, it is equipped with a strongly serrated profile. In addition to transferring torque, it also precisely transfers the cycle times. The units driven by the crankshaft pulley are: Power steering pump, cooling compressor, alternator or generator, possibly brake booster and water pump. On some vehicles, all these units are powered by a single timing belt that also controls the cycle times of two cylinder banks (in V-engines). Therefore, these vehicles, such as Ferrari or Alfa Romeo 164 and 166, are very sensitive when it comes to the timing belt change intervals. Usually, replacement is indicated every 40,000 to 60,000 kilometers. The crankshaft pulley is usually also replaced along with the timing belt.
Detecting crankshaft pulley defects
Crankshaft pulleys very rarely break. Nonetheless, they are usually replaced in the course of a more extensive overhaul. It will announce its failure by uneven rotation that is commonly accompanied by a loud grinding. The reason for this type of wear is unbalanced load of the pulley, especially when idle. As long as this problem "only" affects the pulley that drives auxiliary units, the car can still be operated, provided the noise doesn't cause disturbance. A timing belt pulley should however be replaced as quickly as possible, because otherwise major engine damage may occur. The pulley is usually flange-mounted to the crankshaft with a central M20 nut or larger. There, it can easily be loosened. To prevent it from rotating the engine, it can be blocked at the flywheel (clutch side) with a screwdriver or an allen wrench. If this is not possible, a crankshaft locking tool for approximately 60 euro is required.
When replacing the belt pulley, all other pulleys on the ancillary components ought to be checked. Usually, these are also about to become defective. Naturally, once the belt has been removed, it is not reused but rather replaced by a new one. Also, the belt tensioner and the overrun generator can be checked on this occasion. If the crankshaft pulley has been removed, it is also worth to take a look at the seal located below. The simmer ring is now quite easily accessible. Since replacement of this component is very expensive, a precautionary replacement is recommended on this occasion. A simmer ring puller tool is required, which you can however also borrow from a workshop, if necessary. A new sealing ring on the crankshaft will seal another weak point and potential oil leak in the long run. Crankshaft pulleys by brand manufacturers Crankshaft pulley must withstand one-sided strain at high speeds. Their simple construction makes them a very attractive part for reconstruction by foreign manufacturers. An inferior crankshaft pulley does not visually exhibit its lacking durability. Therefore, buyers should always trust in the quality of brand manufacturers. However, such pulleys are not exactly inexpensive: Even the cheapest crankshaft pulley costs about 70 euro. Quality products by ATEC or CONTITEC can easily have prices exceeding 100 euro.