How to Correctly Judge the Types of Engine Abnormal Sounds and Their Causes

Abnormal sound of the engine is a variety of abnormal metal percussion or other unwanted abnormal sound. When you hear this noise, first use the ear close to the engine to listen carefully, or use a wooden handle screwdriver, metal rods, etc. in different parts of the engine casing to explore the following three points:

    1, the exact location of the voice.

    2, the corresponding relationship between abnormal sound and engine speed, that is, at different speeds corresponding to the level of abnormal sound and whether there is any situation.

    3, the type of abnormal sound characteristics.

Then according to the sound source parts and in different situations, the sound situation correctly determine the type of abnormal sound and its causes.

    1, the top of the piston and the collision of the cylinder head sound: This sound at high engine speeds occur in the cylinder head parts, continuous and crisp and powerful "click, click, click" metal percussion, and the cylinder has vibration. The reason is excessive wear connecting rod bearing and piston pin hole, or pin hole piston pin and connecting rod bearing manufacturing does not meet the requirements, resulting in piston pin and connecting rod bearing or piston pin hole and the pin hole between the too large Or piston head manufacturing ultra-high, which should be disassembled to replace the corresponding parts.

    2, the collision of the piston top and the valve sound: This abnormal noise occurs in the top-mounted valve engine, when the collision, the cylinder head and cylinder head can be heard at a certain interval of time, "click, click, click" Metal clash sound. Low speed time interval long, high speed time interval short, but more serious. The reason is that the locking nut on the adjustment arm of the rocker arm is not tightened, and the bolt is loosened to make the valve gap smaller and to withstand the valve rod end. When the piston in the exhaust process reaches the top dead center, the big end of the valve is hit. In such cases, the valve clearance should be promptly adjusted to tighten the lock nut.

    3, the abnormal sound of the piston ring parts - including the metal percussion ring piston ring, piston ring leakage and excessive coke sound caused by too much.

    (1), the main reason for the piston ring metal percussion is:

Piston ring broken or ring and ring groove gap is too large, or cylinder wall wear to form three steps, the ring and the cylinder wall step collision. The former with a screwdriver in the spark plug short-circuit will be heard off a kind of "唰, 唰, 唰" sound, the latter is a blunt "pop, pop, pop" metal clatter. These two are with the speed increased, the sound increases. This only disassemble repair, replacement of the corresponding parts.

    (2) Piston ring leakage sound is mainly due to: excessive wear piston ring, closing the gap is too large, elastic reduction, poor sealing ring and cylinder or ring openings overlap; groove pulled on the cylinder wall, resulting in the piston ring Blows and sends a hollow

"Drink, drink," "squeak, squeak" sound. This sound with the engine temperature rise will naturally disappear, but the piston ring leakage still need to be ruled out.

    (3) Abnormal sound of excessive coke deposition: This is due to the poor performance of the oil ring and the poor sealing performance, causing the oil to flee into the combustion chamber and form a sharp "chatter" Chatter, "sound, piston ring should be replaced promptly.

    4, knocking cylinder - This is the engine cold start or idling, the piston swinging in the cylinder, the head or skirt collide with the cylinder wall when the cylinder issued a crisp, sharp, "when," or "Dada, da" sound. Knocking cylinder is not a piston failure, but a noise. The reason is:

    (1), Pistons in the cold with larger cylinder clearance, when the cold car starts sound louder, the temperature will be weakened or reduced. No adjustment is needed for this. If the engine temperature is still rising after the sound, while the exhaust pipe and take the blue smoke, then the gap between the piston and cylinder is too large, which may be too much wear on the skirt or cylinder cylinder wear caused by excessive oval Due. Only replace the corresponding parts.

    (2), the engine starts, due to poor lubrication, the piston and the cylinder wall has not yet formed between the oil film and a direct collision knock knock cylinder. When operating for a period of time, the lubrication is normal, the sound decreases or disappears, without any adjustment.

    (3), the mixture can not be normal combustion, resulting in "pre-combustion" or "deflagration", so that the piston and the cylinder wall impact and make a sound, which should make the engine work at normal temperature, clear the cylinder coke, Octane requirements for gasoline.

    (4) When the engine is idling at the moment of no-load rapid acceleration or at high load, the collision sound between the piston and the cylinder wall can be generated when the high-speed gear is in an emergency, and the ignition time should be appropriately delayed to solve the problem.

    5, two-stroke engine cylinder wall scavenging tank has sharp edges, the piston ring thus produces a percussion sound, which should scrub the sharp edges on the wall flatten.

    6, the piston pin and pin hole with too tight, the lower end of the skirt in the direction of the vertical pin hole inward necking, changing the longitudinal profile of the piston skirt, leaving the piston swing when the percussion increased, this should be used Appropriate piston pin and piston into a small gap with the solution to be solved.

    7, Connecting rod bent or twisted. Piston pin and piston pin hole, connecting rod bearing and crank pin misalignment caused by improper piston deflection, resulting in abnormal wear and tear of the cylinder and the resulting knock knock cylinder. This should be corrected or replace the connecting rod to be solved.

In addition there are a variety of abnormal noise, for example:

⑴, connecting rod bulk percussion sound;

⑵, crankshaft parts of the abnormal sound;

⑶, flywheel loose percussion;

⑷, abnormal valve mechanism;

⑸, detonation caused by abnormal sound;

⑹, carburetor throttle abnormal sound.

    These sounds are generally not directly related to the piston, piston ring, not described here.

    Thus, abnormal noise everywhere around the engine, are related to the quality of the manufacture of parts, more related to the conditions of use or the quality of the parts after a certain period of use, to find out the exact cause of the type of sound Be resolved. Really is the piston, piston ring or piston pin caused by the problem of abnormal noise is not much.