What causes the Volkswagen to make abnormal noise at low speed and then disappear?
2 Answers
Volkswagen's low-speed abnormal noise that disappears after a while may be caused by engine idling. The following is a detailed explanation: Engine idling: When the car starts, the idle motion first passes through the crankshaft, then the large flywheel, the clutch, the transmission, the drive shaft, and finally reaches the wheels. When the car starts, the engine's force is transmitted through the crankshaft. First, the transmission's input shaft is connected to the crankshaft, which causes the transmission input shaft to idle when the engine is at idle. However, the input shaft bearing is also rotating, so it generally leads to abnormal noise from the input shaft bearing. No noise when pressing the clutch: In the fault phenomenon, there is no noise when pressing the clutch. When the clutch is pressed, the power cannot be transmitted, and the input shaft bearing will not rotate. If it doesn't rotate, there will be no noise. Therefore, it can be determined that the noise comes from the input shaft bearing. The fault phenomenon shows that the noise returns after releasing the clutch for a while, indicating that the input shaft bearing makes noise when power is transmitted and stops when there is no power transmission.
I had a similar issue with my Volkswagen before, where it would make a squeaking noise at low speeds that would disappear after a while, especially after a cold start. The most common causes are problems with the alternator belt or the A/C belt. When the belts age and become loose, they can slip at low speeds, creating a friction noise that goes away as the temperature rises and the belts expand and tighten. Volkswagen turbocharged models like the 1.8T often experience this issue. Ignoring it for too long can wear out the belt grooves or even lead to a breakdown. Once, during a repair, I found that the water pump belt had a similar noise, which affected the cooling system. I recommend checking the belt tension during regular maintenance and replacing them if necessary—it usually costs just a few hundred bucks. Although it may seem like a minor issue, it poses significant safety risks, so don’t take it lightly. Get it fixed quickly at a reputable shop to avoid potential accidents at high speeds.
