1. Common abnormal sounds and corresponding faults

High frequency "rattling" sound

Possible causes: excessive valve clearance, camshaft or rocker arm wear.

Features: The cold car is obvious when starting, and the frequency increases with the speed.

Check: Open the valve cover to check the clearance (normal value is about 0.05-0.10mm), which requires professional operation.

High-pitched "squeak" friction

Possible causes: belt slip (transmission box), bearing lack of oil (such as axle or starting motor bearings).

Features: The sound is sharp when accelerating, which may be accompanied by power decline.

Check: Check whether the belt of the transmission box is aging and cracking, and whether the bearing is stuck.

A low thump of metal

Possible causes: crankshaft connecting rod wear, loose piston pin, or broken piston ring.

Features: obvious at medium and high speed, may be accompanied by engine vibration intensification.

Danger warning: need to stop immediately, otherwise it may lead to cylinder or crankshaft lock.

Irregular "clatter" noise

Possible causes: clutch shoe wear (transmission box), gear box bearing damage.

Features: The position of the transmission box is abnormal when idling, which may be reduced when accelerating.

Second, scene judgment skills

Abnormal sound during cold startup

The valve clearance is too large, the oil is not sufficiently lubricated (check the oil amount and viscosity).

The abnormal sound continues after the hot car

Piston ring wear, crankshaft bearing problems, may be accompanied by blue smoke (burning oil).

Abnormal sound in a specific speed range

For example, resonance abnormal sound at 4000 RPM: check the exhaust pipe screw loosening or shell resonance.

Third, simple self-test steps

Acoustic localization

Use a long screwdriver to hold different parts of the engine (such as the cylinder head and crankcase), listen to the sound with the ear handle, and determine the source of abnormal sound.

Elimination drive system

Support the big brace, idling the rear wheel, listen to the transmission box is abnormal sound (determine the belt or clutch problem).

Check oil status

Insufficient or deteriorating oil can lead to poor lubrication, resulting in cylinder banging. Check dipstick scale and oil quality.

Fourth, the danger signal that must be stopped immediately

The engine suddenly made a violent metallic crash

Abnormal sound accompanied by power drop, smoke or oil leakage

Unable to start again after extinguishing (cylinder may be pulled)

5. Precautions

Do not confuse normal sound: some models of valve sound, fuel nozzle working sound is a normal phenomenon.

Regular maintenance: Replace the oil and clean the air filter every 2000 kilometers, which can reduce abnormal wear by 80%.

Professional maintenance suggestions: Internal engine disassembly (such as crankshaft and cylinder block) requires professional tools, and it is not recommended to handle by yourself.

If the abnormal sound persists or cannot be determined, it is recommended to record the sound and send it for repair as soon as possible. Early repair costs are typically more than 60 percent lower than after a fault spreads.

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