What causes abnormal noise when starting the car?
1 Answers
Reasons for abnormal noise when starting the car: 1. Worn hydraulic tappets or system pressure loss: Under normal circumstances, hydraulic tappets are always filled with engine oil at a certain pressure to ensure zero valve clearance, preventing valve noise during operation. 2. Insufficient lubrication system pressure: Or severely worn hydraulic tappets where the internal pressure is inadequate to support the plunger, leading to increased valve clearance and producing a tapping sound from the valves during engine operation. 3. Severely worn hydraulic tappets: When the car is parked for an extended period, oil leaks out from the hydraulic tappets. During the first start, insufficient oil inside the hydraulic lifters results in a tapping sound from the valve stems hitting.