What Causes the Metallic Friction Sound in Engine Abnormal Noise?
2 Answers
This could be the sound coming from the valves. During cold starts, both the water and oil temperatures are low. If the viscosity and lubrication of the engine oil are insufficient, the lifters cannot adjust properly, resulting in a metallic friction sound during cold starts. More possible causes are as follows: 1. Hydraulic lifter issue: There are many reasons for metallic sounds. First, it could be due to the hydraulic lifters—either the oil pressure is too low or the hydraulic lifters themselves are worn. Once air enters the lifters, a metallic friction sound will occur when starting the car. 2. Throttle issue: If the valve rocker arms are worn, causing excessive clearance, or if there is too much sludge or carbon buildup, a dirty throttle can also cause a metallic sound during cold starts. 3. Engine front cover issue: Another possibility is improper assembly of the engine front cover. During cold starts, the output power increases, leading to louder engine noise, which is normal. However, if the noise is excessively loud, you can mention this situation during maintenance.
Oh, I've encountered this situation before - that metallic grinding sound from the engine is truly hair-raising. Usually it's caused by direct metal-to-metal contact between internal components, like worn piston rings or crankshaft bearings. When the engine oil can't keep up over time and lubrication becomes insufficient, it produces that harsh scraping noise. Loose or worn-out belts/chains can also cause noise easily, especially when the car has been driven for long periods or in hot weather - thermal expansion worsens the friction. When I used to drive an old car, any loud noise meant I had to pull over immediately and check the dipstick. If oil level was low, I'd try adding some quality oil, but never delay - drive straight to the mechanic for thorough inspection. Unresolved abnormal noises could mean complete engine failure, with repair costs running into tens of thousands. Regular maintenance is key - things like oil changes and belt inspections once a year can prevent problems before they occur.
