There are several possible causes of seal failure in automotive applications, including:

Contamination: Dirt, debris, or other particles can get into the sealing interface and cause damage or wear to the seal.

Improper installation: If the seal is installed incorrectly, it may not be able to create an effective seal or may become damaged during installation.

Chemical exposure: Exposure to certain chemicals, such as fuels, oils, or solvents, can cause degradation or swelling of the seal material, leading to failure.

Temperature extremes: Extreme temperatures can cause seals to become brittle or degrade, which can lead to failure.

Wear and tear: Over time, seals can wear down due to normal use, which can cause leaks or other problems.

Age: Even if a seal is not used or exposed to any adverse conditions, it can still degrade over time due to the effects of age.

It's important to identify the cause of seal failure and take steps to address it, such as replacing the seal, changing the installation process, or using a different seal material that is more resistant to the cause of failure.