What Causes the Hissing Sound from the Engine?

1 Answers
Arthur
07/24/25 10:57pm
Engine hissing sound may be caused by the following reasons: 1. Engine Overheating: It is necessary to promptly inspect the vehicle, check the cooling system, and resolve the abnormal noise. 2. Exhaust System Blockage or Vacuum Tube Leakage: Immediately visit a 4S shop to inspect the exhaust system and vacuum tubes. Additional information about other abnormal noises: 1. During engine operation, if a hissing sound is heard at the carburetor intake air filter, it indicates air leakage at the intake valve. 2. If a hissing sound is heard at the exhaust pipe or muffler, it indicates air leakage at the exhaust valve. Specific causes of valve leakage are as follows: 1. Wear or corrosion on the working slope of the valve and valve seat, resulting in spots, pits, or carbon deposits. 2. Excessive clearance between the valve stem and valve guide sleeve, causing the valve stem to wobble and preventing proper valve closure. Alternatively, bending or deformation of the valve stem or misalignment of the valve head may lead to incomplete closure and air leakage, resulting in a hissing sound. 3. Weakened or lost elasticity of the valve spring, or spring breakage, causing improper sealing between the valve and valve seat. 4. Insufficient valve clearance. When the valve stem expands due to heat, the tappet or rocker arm may push the valve open, preventing complete closure and causing air leakage noise.
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