WHEN THE ENGINE MALFUNCTIONS, THE CAR WILL EXHIBIT DIFFERENT PHENOMENA, AND ABNORMAL NOISE IS ONE OF THEM. IT IS OFTEN A MANIFESTATION OF CERTAIN FAULTS, AND IF NOT ELIMINATED IN A TIMELY MANNER, IT WILL ACCELERATE THE WEAR AND TEAR OF THE PARTS, AND EVEN CAUSE ACCIDENTAL DAMAGE. THEREFORE, IT IS NECESSARY TO MAKE TIMELY JUDGMENTS AND TAKE NECESSARY MAINTENANCE MEASURES TO ELIMINATE FAULTS. CHECK FOR ABNORMAL ENGINE NOISE MANUAL VISUAL INSPECTION METHOD CAN BE ADOPTED 1. LOOK: OBSERVE THE CONDITION OF THE MECHANISM, ASSEMBLY, AND PARTS WITH SUSPECTED FAULTS TO DETERMINE THE WORKING CONDITION OF THE ENGINE. 2. TOUCH: TOUCH THE TEMPERATURE AND VIBRATION OF THE POSSIBLE FAULTY AREA WITH YOUR HAND TO DETERMINE FACTORS SUCH AS THE TIGHTNESS OF THE FIT, THE SIZE OF THE BEARING CLEARANCE, AND THE BALANCE OF THE PART WEIGHT. 3 TESTS: VARIOUS TESTING METHODS ARE USED TO FULLY DEMONSTRATE THE FAULT PHENOMENON, SUCH AS HONKING THE HORN, TURNING ON THE IGNITION SWITCH OR LIGHT SWITCH, "CUTTING OFF" THE SPARK PLUG, RAPIDLY INCREASING OR DECREASING THE ENGINE SPEED, ETC. IF NECESSARY, THE ASSEMBLED ASSEMBLY OR PARTS CAN ALSO BE REPLACED FOR COMPARATIVE TESTING. 4. LISTEN: DETERMINE WHICH SOUNDS ARE NORMAL AND WHICH ARE ABNORMAL BASED ON THE SOUNDS AND PATTERNS PRODUCED BY THE ENGINE IN DIFFERENT WORKING CONDITIONS AND PARTS. IF IT IS CONFIRMED THROUGH THE ABOVE OBSERVATION, TOUCH, TEST, AND LISTENING THAT THE ENGINE IS MAKING ABNORMAL NOISE, THEN THE NEXT STEP IS TO IDENTIFY WHAT FAULT IT IS. BELOW, KANG GE HAS COMPILED THE "FOUR LISTENING" TIPS TO HELP YOU EASILY IDENTIFY ENGINE FAULTS: REMEMBER THE "FOUR LISTENS" TO EASILY IDENTIFY ENGINE FAULTS VALVE FOOT NOISE PHENOMENON☑ WHEN A DIESEL ENGINE IS COLD STARTED, NOISE IS PRONE TO OCCUR.☑ THE SOUND IS NOT RELATED TO THE ROTATIONAL SPEED, BUT OCCASIONALLY PRODUCES A CRISP SOUND THAT QUICKLY DISAPPEARS. IN SEVERE CASES, THIS SOUND WILL APPEAR FREQUENTLY.☑ WHEN THE SOUND APPEARS, SOME CYLINDERS DO NOT WORK, AND AFTER THE SOUND DISAPPEARS, IT WILL RETURN TO NORMAL. REASON☑ THE LOOSENESS CAUSED BY INSUFFICIENT INTERFERENCE FIT BETWEEN THE VALVE SEAT RING AND THE CYLINDER HEAD.☑ THE MATERIAL USED FOR THE VALVE SEAT RING IS INAPPROPRIATE, AND THE COEFFICIENT OF THERMAL EXPANSION IS TOO SMALL. DIAGNOSIS AND EXCLUSION☑ WHEN A SOUND APPEARS, THERE IS A PHENOMENON OF INDIVIDUAL CYLINDERS NOT WORKING; IF THE SOUND DISAPPEARS AND THE DIESEL ENGINE RETURNS TO NORMAL, IT CAN BE DIAGNOSED THAT THE VALVE SEAT RING OF THE NON WORKING CYLINDER IS LOOSE.☑ USE A CYLINDER PRESSURE GAUGE TO MEASURE CYLINDER PRESSURE ONE BY ONE, AND THE CYLINDER WITH LOW PRESSURE IS THE ONE WITH ABNORMAL NOISE. CAMSHAFT NOISE PHENOMENON☑ WHEN THE DIESEL ENGINE IS RUNNING AT MEDIUM SPEED, THERE IS A LOUD NOISE COMING FROM THE CAMSHAFT SIDE OF THE CYLINDER BLOCK; THE SOUND IS CHAOTIC AND UNCLEAR AT HIGH SPEEDS.☑ WHEN A SINGLE CYLINDER LOSES FUEL, THE SOUND REMAINS UNCHANGED.☑ VIBRATION IS PRESENT NEAR THE CAMSHAFT BEARINGS. REASON☑ THE CLEARANCE BETWEEN THE CAMSHAFT BEARING AND THE JOURNAL IS TOO LARGE AND LOOSE.☑ LOOSE CAMSHAFT BEARINGS OR EXCESSIVE EROSION, PEELING, OR WEAR OF BEARING ALLOYS.☑ THE AXIAL CLEARANCE OF THE CAMSHAFT IS TOO LARGE OR THE CAMSHAFT IS BENT. DIAGNOSIS AND EXCLUSION☑ USE A STETHOSCOPE TO LISTEN TO THE SOUND ON THE CYLINDER OF THE DIESEL ENGINE AT THE HIGHEST SPEED. IF THERE IS A STRONG SOUND ACCOMPANIED BY VIBRATION IN A CERTAIN AREA, IT CAN BE DIAGNOSED AS BEARING NOISE AT THAT LOCATION.☑ IF THERE IS NO CHANGE IN THE SOUND DURING THE FUEL CUT-OFF TEST, THE THROTTLE VALVE CAN BE SLOWLY CHANGED. IF THE IDLE SOUND IS CLEAR, THE SOUND IS OBVIOUS AT MEDIUM SPEED, AND THE SOUND CHANGES FROM CHAOTIC TO REDUCED AT HIGH SPEED, IT CAN BE DIAGNOSED AS EXCESSIVE AXIAL CLEARANCE OF THE CAMSHAFT OR LOOSE BEARINGS. VALVE LEAKAGE PHENOMENONWHEN A MALFUNCTION OCCURS, DIESEL ENGINES MAY HAVE DIFFICULTY STARTING, EXHAUST PIPES MAY EXPLODE AND SMOKE, FUEL CONSUMPTION MAY INCREASE, AND ABNORMAL NOISES MAY BE EMITTED. REASON☑ THE WORKING SURFACE OF THE VALVE AND VALVE SEAT RING IS WORN, ERODED, AND POORLY SEALED, RESULTING IN AIR LEAKAGE.☑ THE WORKING SURFACES OF THE VALVE AND VALVE SEAT RING HAVE CARBON DEPOSITS, AND THE VALVE IS NOT TIGHTLY CLOSED, RESULTING IN AIR LEAKAGE.☑ THE CLEARANCE BETWEEN THE VALVE AND THE VALVE GUIDE IS TOO LARGE, CAUSING THE VALVE STEM TO SHAKE, RESULTING IN LOOSE CLOSING OF THE CONNECTING VALVE AND AIR LEAKAGE.☑ THE VALVE STEM BECOMES STIFF OR STUCK INSIDE THE VALVE GUIDE, PREVENTING THE VALVE FROM MOVING UP AND DOWN.☑ THE VALVE SPRING LOSES ELASTICITY OR THE SPRING BREAKS. DIAGNOSIS AND EXCLUSIONAFTER RULING OUT THE CAUSES OF IGNITION AND FUEL SYSTEM FAULTS, IT IS STILL UNCERTAIN WHETHER MEASURING CYLINDER PRESSURE, MEASURING CYLINDER PRESSURE OR INTAKE MANIFOLD VACUUM CAN ACCURATELY DETERMINE THE FAULT. WHEN MEASURING CYLINDER PRESSURE, THE CYLINDER WITH VALVE LEAKAGE HAS A LOWER PRESSURE THAN OTHER CYLINDERS. HYDRAULIC TAPPET NOISE PHENOMENONWHEN THE DIESEL ENGINE IS RUNNING, THERE IS A RHYTHMIC SOUND, WHICH IS OBVIOUS AT IDLE AND WEAKENS OR DISAPPEARS ABOVE MEDIUM SPEED. REASON☑ THE LUBRICATING OIL PAGE OF THE DIESEL ENGINE IS TOO HIGH OR TOO LOW, CAUSING THE LUBRICATING OIL WITH BUBBLES TO ENTER THE HYDRAULIC TAPPET, FORMING ELASTIC GAS AND GENERATING NOISE.☑ THE LUBRICATING OIL PRESSURE IS TOO LOW.☑ THE LUBRICATING OIL PUMP AND FILTER ARE DAMAGED OR BROKEN, CAUSING AIR TO BE SUCKED INTO THE LUBRICATING OIL.☑ HYDRAULIC STRUT FAILURE.☑ USE LOW-QUALITY LUBRICATING OIL. DIAGNOSIS AND EXCLUSION☑ CHECK THE LUBRICATING OIL LEVEL, ADD OR REPLACE AS NECESSARY, AND KEEP THE OIL LEVEL IN A NORMAL STATE.☑ CHECK IF THE LUBRICATING OIL PRESSURE IS NORMAL AND IF THE HYDRAULIC TAPPET IS MALFUNCTIONING.☑ DISASSEMBLE THE OIL PAN TO INSPECT THE LUBRICATING OIL PUMP, FILTER, AND REPLACE THE LUBRICATING OIL PUMP; DISASSEMBLE AND INSPECT THE VALVE MECHANISM, REPLACE THE HYDRAULIC TAPPET AND VALVE GUIDE.