What is the engine valve clearance?
2 Answers
For diesel engines, the intake valve clearance is 0.25-0.30 mm, and the exhaust valve clearance is 0.30-0.35 mm. Most valve clearance parameters range between 0.15-0.4 mm, with the optimal adjustment being between 0.2-0.35 mm. More details are as follows: 1. Valve clearance is set to ensure the proper functioning of the internal combustion engine's valve train. Since the valve train operates at high speeds and elevated temperatures, components such as valve lifters and valve stems expand when heated. This can automatically open the valve, preventing it from sealing tightly against the valve seat and causing leakage. 2. To prevent this phenomenon, during the design of the valve train, a certain gap is maintained between the end of the intake and exhaust valve stems and the adjusting screw on the lifter (or rocker arm). This gap is known as the valve clearance.
I used to drive an old car, and the engine always made a loud ticking noise. When I took it to the repair shop, the mechanic said the valve clearance was a bit too large. The normal valve clearance is generally around 0.2 to 0.4 millimeters, but my car measured over 0.5 millimeters, so he spent some time adjusting it for me. He reminded me that the gap varies significantly between different car models. For example, a Toyota might only need 0.3 millimeters, while some German cars might require between 0.15 and 0.25 millimeters. If the clearance is too large, the noise affects driving comfort; if it’s too small, the valves might seize when the car heats up. It’s best to check it every 30,000 kilometers. Later, I looked up the manual online and found that the manufacturer’s recommended value is crucial and shouldn’t be ignored. After the adjustment, the car ran much better, and there were no strange noises even on the highway.
