FAA Powerplant Written Practice Test

When cleaning aluminum and magnesium engine parts, why is it inadvisable to soak them in solutions containing soap?

1. It will damage the aluminum surface

2. It will cause rust

3. Soap can cause engine oil contamination and foaming

4. It will make the parts slippery

The correct answer is: Soap can cause engine oil contamination and foaming

Soaking aluminum and magnesium engine parts in solutions containing soap is inadvisable primarily because soap can lead to engine oil contamination and foaming. Soap is composed of surfactants that can create a film on surfaces. When these surfaces come into contact with engine oil, the soap's residue can mix with the oil, potentially leading to oil degradation and increased foaming during operation. Foamy oil can compromise lubrication, resulting in poor engine performance and increased wear on engine components. Additionally, while it's important to consider that certain cleaning methods might affect the integrity of aluminum or magnesium surfaces over time, the immediate issue with soap lies in its propensity to contaminate and degrade oil performance. Therefore, using solvents specifically designed for cleaning engine parts, which do not leave harmful residues, is recommended to ensure the proper functioning and longevity of engine components.