求翻译：4．避免单向阀、通气阀堵死。由此引起箱壳内温度升高，油气充满整个空间、排放不出去，使箱壳内压力升高润滑油消耗增加和更换周期缩短。发动机通气系统堵塞后，增加了活塞的运动阻力，使油耗增加。由于箱壳内外气压差的作用，往往会引起密封薄弱处漏油。因此需对车辆进行定期检查、疏通、清洗。是什么意思？

4. Avoid the trap, vent valve blocked. Resulting high temperature inside the box, hydrocarbon emissions does not fill the space, so elevated pressure in the tank shell lubricating oil consumption increased, and shortening the replacement cycle. Engines after blocking the ventilation system, increased resistance to motion of the piston, to increase the fuel consumption. Role of internal and external air pressure difference due to the tank shell, weak tends to seal oil leak. Therefore need regular check of the vehicle, dredging and cleaning.