Can Water Enter the Transmission Vent Plug?
2 Answers
Transmission vent plugs can allow water ingress. Below are three levels of water intrusion in transmissions: Severe Water Intrusion: This can be identified by observing the oil-water mixture. If the transmission has significant water ingress, it can be directly observed during oil drainage. Specifically, drain the transmission fluid—if there is substantial water ingress, the color and viscosity of the oil-water mixture will indicate the severity. Moderate Water Intrusion: White deposits in the oil pan suggest moderate water intrusion. If oil drainage alone doesn't confirm water ingress, further inspection is needed. This involves removing the oil pan for observation. When water mixes with transmission fluid, it forms a white emulsion that adheres to the oil pan. The presence of such deposits confirms moderate water intrusion. Mild Water Intrusion: Partial rusting of internal screws indicates mild water intrusion. If the above methods don't yield conclusive results, disassemble the transmission to inspect the screws. Water-oil mixture corrodes steel screws, so rusted screws confirm mild water intrusion with relatively low water content.
As someone who has driven for many years, I know that transmission vent plug water ingress can indeed happen, especially during water wading. The vent plug is designed to balance internal transmission pressure, not to be fully sealed. In areas with high water pressure, water can easily flow backward into it, such as when driving through deep puddles or flood zones. Once water enters, it mixes with the oil, causing emulsification and deterioration, leading to lubrication failure, clutch slippage, or even internal component damage. I've seen many car owners spend a fortune on repairs because of this issue. It's advisable to avoid driving in high water levels and to check the transmission oil color after rain. If it appears milky or foamy, take it to a professional shop immediately. Better safe than sorry—don't risk damaging major components for temporary convenience.
