What Causes the Screeching Sound at the Moment of Engine Start?

[CalvinDella]

Engine oil temperature being too low is the reason for the screeching sound at the moment of engine start. Here is the relevant information: Cause: When the engine oil temperature is too low, various components inside the engine lack lubrication, resulting in increased friction between them. Consequently, some abnormal noises may occur, which is a normal phenomenon. Function: Engine oil is referred to as the lifeblood of the engine. Inside the engine, it not only lubricates but also cleans, seals, cushions, prevents rust, and dissipates heat. During engine operation, the oil forms a thin film on the surfaces of various components, preventing direct contact and friction between them.

[McJocelyn]

Last time my car made a screeching noise during startup, the mechanic said it was the starter's one-way clutch slipping. It happens when the starter's small gear can't properly engage with the engine flywheel, causing friction and that grinding sound. This issue mostly occurs in older vehicles and is particularly noticeable during cold starts. Additionally, when the starter's carbon brushes are nearly worn out, they can produce a similar metallic screeching sound. I'd recommend getting your starter checked soon. Putting off repairs might lead to sudden failure to start - I got stranded in a supermarket parking lot last time and had to call a tow truck, which was both costly and inconvenient.

[DiJuniper]

That screeching sound during startup is most likely a slipping belt. After running an auto repair shop for twenty years, I've seen this as the most common issue in older cars. When you turn the key, accessories like the alternator and A/C compressor start spinning, and if the belt has hardened with age or gotten oil contamination, it'll slip. Here's a quick test: sprinkle some water on the belt at startup—if the noise disappears immediately, you've confirmed belt trouble. Avoid soapy water though, as alkaline substances accelerate belt deterioration. Belts typically last five years or 80,000 km; beyond that, weird noises become likely. A failing tensioner pulley bearing can also cause screeching—in such cases, replacing the entire set is the safest fix.

[BrielleRose]

Oh man, I just had this happen last month! That screeching sound during cold startup made me drop my phone. Took it to the dealership and they diagnosed it as insufficient lubrication in the power steering pump bearing. The technician explained that the ball bearings inside the pump pulley were grinding dry, and the noise occurs during cold starts when the load is highest. They applied special grease as a temporary fix which stopped the noise, but warned that the damaged bearing might eventually require a full pump replacement. Pro tip: Pay attention to the noise location - left side engine noise could indicate AC compressor bearing issues, while right side noise often points to alternator bearing problems. Turbocharged owners should additionally check for stuck turbocharger bypass valves.

[DiGenevieve]

New car owners should pay special attention to these abnormal noises! There are three common mechanical faults that cause screeching sounds: first, the starter motor's bendix gear getting stuck; second, the rubber damping layer of the crankshaft pulley aging and cracking, causing slippage. The most troublesome issue is when the timing chain tensioner leaks oil - during cold starts, the chain slapping against the guide rail produces a metal scraping sound. Once when I was driving overnight, this noise suddenly became louder. After pulling over to check, I found the oil dipstick showed empty. I barely made it to the repair shop after adding oil. I recommend everyone develop the habit of listening to the engine sound during warm-up. If abnormal startup noises persist for more than three days, get it inspected immediately - don't take risks like I did.

[DiAlexander]

This kind of sudden abnormal noise is mostly caused by improper installation of components. Last year, when I helped my brother repair his car, we encountered a similar issue: after replacing the alternator, there was always a screeching sound upon startup. Upon inspection, it was found that the mechanic had forgotten to install the retaining washer for the belt idler pulley, causing axial movement of the wheel. Additionally, a loose battery terminal can produce an arc discharge sound, resembling the tearing of cloth. For modified cars, it's important to check if the grounding wires are loose. In fact, the quickest diagnostic method is to open the hood and start the engine twice: have someone turn the key while you listen closely to the engine. If the sound comes from the top, it's usually a starter issue; if it's from the bottom, it's likely a belt system failure, and if it's from the side, focus on checking the alternator bracket screws.