What Causes the Friction Sound in the Engine?
2 Answers
Engine friction sounds may originate from the valves. During cold starts, when both the water and oil temperatures are low, if the viscosity and lubrication of the engine oil are insufficient, the tappets cannot adjust properly, resulting in metal friction sounds during cold starts. Causes of Engine Valve Noise: The primary cause of engine valve noise is excessive valve clearance, especially after engine cleaning by the owner. Other factors include severe wear on the camshaft or valve lifters, causing the tappets to jump and strike the valves during operation, as well as excessive oil viscosity and insufficient oil volume. Function of Engine Valves: Valves are responsible for introducing fuel into the engine and expelling exhaust gases. Traditional engines have one intake valve and one exhaust valve per cylinder. This design is relatively simple, cost-effective, easy to maintain, and performs well at low speeds. However, its drawback is the difficulty in increasing power, especially at high speeds, where the air intake efficiency is low, leading to weaker performance.
As a car owner, I've encountered similar issues. Friction sounds from the engine usually indicate that certain components are rubbing or lacking lubrication. The most common cause is belt problems, such as aging or loose alternator belts or AC belts, causing them to slip on the pulleys and produce squeaking noises. Additionally, worn bearings are often the culprit, such as faulty water pump bearings or AC compressor bearings, which create metal-on-metal friction when rotating. Sometimes, it's due to insufficient internal engine lubrication caused by old or degraded engine oil, reducing the cushion between components. Ignoring these sounds can lead to engine overheating, sudden belt failure stranding you on the roadside, or complete bearing failure requiring expensive repairs. Therefore, I recommend first stopping the car and conducting a basic inspection: start the engine and listen for the source of the friction noise. If it's coming from the belt area, try adjusting the tensioner. If the sound seems deeper, it's best to consult a professional mechanic with a stethoscope for diagnosis. Regular maintenance can prevent this issue—check belts and bearings during every oil change to extend their lifespan and save money in the long run. In short, safety first—don't wait until the friction sound turns into a roar before taking action.