The serpentine belt drives the accessories of the powertrain and comfort systems on 21st century cars. They are equipped with a belt tensioner that keeps the belt firm in its position. Belts, like other mechanical components must be replaced after a specific period of time. The belt tensioner wears down when it experiences longer loading periods. Thus, the tensioner needs to be replaced due to the problems arising from various reasons.
The automatic tensioner is held in position with a coil spring. The belt tensioner provides some free movement to absorb shock loads generated by the A/C compressor during the immediate starting up of auxiliary components. The tensioner keeps the belt under constant tension.
The tensioner should be checked regularly. If it is damaged or not providing the required belt tension, the results can be any of the following: Belt slippage, belt failures and excessive wear of belts. Often customers consider this as a failure of the belt drive and replace the belt. But the problem lies in the fact that the tensioner is worn out and it causes the failure of the belt. As a result, torque supplied to the auxiliary components is stopped abruptly such as to the power steering, the alternator and the water pump. When the water pump shaft stops rotating, the flow of coolant stops and this leads to overheating of the engine. When the alternator shaft stops rotating, there is no output from the alternator and the battery starts to run down. When the power steering pump stops turning, the steering becomes stiff and hard to steer.
Belt tension is crucial to the proper functioning of the drive. Less tension may cause the belt to slip and squeal. Slippage causes additional heat generation on the belt. Too little tension may result in the belt coming loose from its pulleys. Too much tension on a belt may overload the belt as well as the shaft bearings on the water pump, alternator, power steering pump and air conditioning compressor, possibly leading to premature failures in these components. Therefore, the tensioner is of critical importance to meet the working requirements.
Symptoms of a Worn-out Belt Tensioner
Belt Slippage: Belt slipping can be caused by less spring tension on the tensioner. The tensioner arm movement is checked during engine idle as and when some of the auxiliary components are turned on and off. The tensioner may be stuck if the tensioner pulley doesn’t move at all. A worn damper can cause tensioner arm oscillation when the engine is idling. Slipping of belt results in the alternator not charging up quickly as required and battery power goes down.
Belt Fluttering: As the spring inside, the tensioner becomes weak due to regular loading, it results in too much of movement of the tensioner pulley.
Belt or tensioner noise: Any squealing or rubbing noises should be examined to find the exact cause of the noise. A probe mechanism is used to find the noise arising from the tensioner pulley.
Pulley damage: This may be caused due to excessive tension on the automatic tensioner pulley. If the pulley is damaged, replace the tensioner assembly not just the pulley. If an idler pulley is damaged, inspect the tensioner also because vibrations caused by a bad idler pulley may damage the tensioner.
The above symptoms require an immediate replacement of the tensioner. If it is not replaced, it can have a detrimental effect on auxiliary components and may even lead to its failure.