What Causes Oil Leakage from the Transmission Vent Hole?
2 Answers
Automobile transmission oil leakage can be caused by the following reasons: 1. Causes of oil leakage at the oil seal shaft neck: The oil seal may become aged and deformed, the oil seal spring may fall off, or the oil seal may be installed in the wrong direction, all of which can cause the oil seal to lose its oil-blocking function. In such cases, the aged and deformed oil seal should be replaced, and attention should be paid to the installation direction of the oil seal—the side with the spring ring should face the oil side. If the shaft neck is worn or dented, causing an improper fit with the oil seal and resulting in leakage, the worn or dented shaft neck should be replaced or repaired. 2. Pipeline damage: If the pipeline is damaged, oil may leak from the damaged area during circulation. 3. Causes of oil leakage at the joint surface of the transmission case: If the joint surface of the transmission case is damaged, an appropriately thicker paper gasket should be added at the damaged area. If leakage persists, welding and repair should be performed. If the sealing paper gasket is damaged, it should be replaced with an identical one. If the transmission case cover screws are loose, they should be tightened promptly.
I've seen cases of oil leaking from the transmission vent quite a few times, mostly caused by overfilled transmission fluid or internal issues. When there's too much oil, it expands due to heat during operation, and the increased pressure can force oil out through the vent - just like steam escaping from a boiling kettle. It could also indicate worn internal components, such as deteriorated seals or damaged shaft seals, allowing fluid to leak where it shouldn't. Another possibility is a clogged ventilation system preventing proper air release. Never delay addressing this issue. First, I'd park the vehicle and wait 30 minutes for the oil to cool before checking the fluid level. If oil still leaks when the fluid level is correct on a cold engine, it likely indicates a serious problem requiring professional repair. Untreated, this can lead to transmission overheating and failure, resulting in repair bills running into thousands. My advice: regularly check fluid levels and avoid overfilling during oil changes to prevent this headache.
