What causes the crank seal to leak?

A crank seal can leak due to several factors, including wear and tear over time, which can cause the seal material to degrade or harden. Additionally, excessive engine pressure or improper installation can lead to seal failure. Contaminants such as dirt or oil sludge can also damage the seal, further contributing to leaks. Lastly, engine vibrations and misalignment may compromise the seal's effectiveness, leading to oil leaks.