What Causes Abnormal Noise During Engine Idle?
4 Answers
Engine idle abnormal noise causes are as follows: Balance shaft wear: The balance shaft is used to reduce vibrations generated during engine operation. If the balance shaft oil passage becomes blocked, it will increase wear on the journal and bearings, leading to abnormal noise. Connecting rod bearing wear: If the vehicle is filled with inferior engine oil, excessive sludge may form, blocking the lubrication oil passage and preventing oil from reaching components that require lubrication and cooling. This can cause wear on the camshaft, crankshaft, and connecting rod bearings, resulting in abnormal noise. Variable timing gear clearance increase: Variable valve timing can adjust according to engine speed and operating conditions, typically using hydraulic control of the camshaft timing gear's internal rotor to achieve a certain degree of advance or delay. If the internal rotor of the variable timing gear becomes stuck or the oil chamber wears, it will lead to increased clearance and abnormal noise.
I've only been driving this car for a few years, but I've encountered abnormal noises at idle several times, most commonly issues with the belt. Once, my car made a ticking sound, and upon careful inspection, it turned out the fan belt was loose or worn, causing friction against the wheel during operation. Other times, it was the water pump bearing wearing out, producing a buzzing sound like an old fan struggling to turn. Engine internal problems are also significant, such as insufficient oil, leading to poor lubrication between components and resulting in harsh grinding noises. Also, consider cracks in the exhaust system, loose valve plates causing ticking sounds, or excessive piston clearance leading to knocking noises. These issues shouldn't be ignored. I once neglected it, and delaying the repair only cost me more to fix the tensioner later. It's best to stop the car steadily at idle, listen for the source of the noise, and then head straight to a professional shop for inspection. Regular maintenance should also pay attention to belt tension and oil levels to avoid shortages—safety first to prevent accidents on the road.
I've been driving for over a decade, and idle speed noises are mostly caused by mechanical looseness. For example, aging or slipping fan belts produce annoying buzzing and squeaking sounds; damaged bearings in the water pump or alternator create a whining noise; and loose pulley wheels make a drum-like tapping sound at idle. Internal factors include insufficient engine oil causing loud friction noises that can startle you; leaking exhaust joints produce hissing sounds; and valve train issues result in constant tapping. I recommend starting with simple checks like inspecting belts for cracks or misalignment. Ignoring these issues can lead to severe engine damage and costly repairs. Regular maintenance, such as timely oil changes for proper lubrication, prevents minor issues from becoming major problems. If you hear unusual noises, stop the car immediately without revving the engine and have a reliable technician use proper tools to diagnose and ensure safe driving conditions.
Last time when my car was idling, there was a strange noise that really startled me. Later, I asked a friend and learned that common causes include a loose fan belt, which squeaks annoyingly; or a water pump issue causing a humming sound; and when the engine oil is low, the engine makes a harsh grinding noise. Don’t take it lightly, as such noises could lead to the alternator failing, which is really troublesome. That time, I quickly pulled over to check and eventually found out the belt needed replacing. My advice is to go to a repair shop as soon as you notice a problem—it saves trouble and gives peace of mind. For regular maintenance, pay attention to the belt condition and oil level to prevent issues.
