How to identify engine failure?

October 20, 2019

The engine is called the "heart" of the car. If a part is damaged, it is not only expensive to maintain but also particularly costly. When an abnormal situation occurs in the engine, it must be discovered and dealt with in a timely manner to prevent it from having a bigger problem. Once the minor problems in the engine have been amplified, the entire part must be replaced. How to identify engine failure? China Automotive Network Xiaobian to help.


Listen: Valve leakage

In the event of a failure, the engine will be difficult to start, the exhaust pipe will emit fire, smoking, increased fuel consumption, and abnormal sound. The main causes of these phenomena are the erosion, ablation, and poor sealing of the working face of the valve and valve seat ring, and the carbon deposition on the working face of the valve and valve seat ring; the leakage of the valve is not strict; the clearance between the valve and the valve guide is too large. The valve stem rattles, resulting in loose air close to the closed air valve. The valve stem is astringent or stuck in the valve guide and the valve cannot move up and down. The valve spring loses its elasticity or the spring breaks.

How to troubleshoot?

After eliminating the causes of failures in the intake and exhaust systems and the fuel system, it is not yet possible to determine the cylinder pressure at the time of failure, and the cylinder pressure or the intake manifold vacuum level can be determined. This can be determined more accurately. When the cylinder pressure is measured, the valve is leaking. The cylinder pressure is lower than other cylinders.

Two listen: camshaft ring

When the engine is idling, the sound is clear, the sound is pronounced at medium speed, and the sound at high speeds is reduced from clutter to loss, which can be determined as camshaft sound. Abnormal wear of the camshaft results in an increase in the clearance between the camshaft and the bearing housing, and an axial displacement occurs when the camshaft moves, resulting in abnormal noise. Abnormal wear also results in an increase in the clearance between the drive cam and the hydraulic tappet. When the cam is combined with the hydraulic tappet, an impact occurs and an abnormal sound is generated.

How to troubleshoot?

Make the engine auscultate with the stethoscope under the strongest speed of the sound, if there is a strong sound and accompanied by vibration, it can be diagnosed as the bearing in the place. If the idling sound is clear, the sound is pronounced at medium speed, and the noise is reduced by clutter at high speeds, the camshaft can be diagnosed as having too large axial clearance or loose bearings.

Editor's Note: When driving a car, drivers must learn to judge the abnormal sound of the car engine. If you hear a clatter, you must pay attention. Don’t hear it, but keep driving in the car. That will only have more serious consequences.

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