"A good knock will come out", - auto mechanics joke when they cannot immediately determine the cause of extraneous noise in the operation of the car. But it is impossible to endure, even while in the cabin, how piercingly whistles under the hood. Why can a seemingly new alternator belt whistle?
What is this belt for?
The alternator belt connects the vehicle's alternator to the engine's crankshaft. During engine operation, when the shaft rotates, its rotation is transmitted through this belt to the generator rotor. The generator, generating direct current, distributes it to all systems of the car and, along the way, constantly recharges the battery. In the event of a belt break, the alternator stops supplying power to the systems in need, including the air conditioner, the battery will soon run out and the vehicle will no longer be able to move.
On some models (for example, on domestic cars), the same belt rotates the blades of the engine cooling fan. Therefore, a belt burst is fraught with instant overheating and boiling of the coolant.
Where does the whistle come from?
If, while sitting in the passenger compartment, you hear a thin squeak or whistle on one note while driving, then most likely it is the alternator belt whistling. The belt runs through pulleys mounted on the engine and generator shafts. The belt is made of synthetic materials, the pulleys are metal. Their contact at the moment of slipping causes such a peculiar non-metallic sound.
Why whistles and what to do
The first thing that comes to mind when the belt whistled is its extreme wear. Yes, this is the likely reason. Disheveled, it can whistle when rotating. In this case, the belt must be replaced urgently. A little more, and it will burst.
Always keep a replacement alternator belt from an approved manufacturer in your trunk. A belt purchased compelledly or by someone suggested in a desperate moment may simply not fit your car.
But the whistle can appear even with a perfectly suitable belt. Most often, this is its weakened tension, as a result of which the belt begins to slip and emit a whistle. Tension the belt by loosening the retaining nut and sliding the generator back. On some cars, this is done using a tension roller.
If the required tension cannot be achieved, then the belt is already stretched to the limit and should be replaced.
Finally, the cause of the whistling sound may be belt slipping due to oil, antifreeze or other technical fluids on the pulleys. Thoroughly wipe the belt and pulleys and remove the possibility of contamination with foreign matter.
