Under what condition would the power steering fluid level be considered a failure?

The power steering fluid level is considered a failure when it is below 1 inch of the manufacturer's recommended level. This is because having an insufficient fluid level can directly impair the functioning of the power steering system, potentially leading to steering difficulties, increased wear on the system, and even failure to steer properly. The manufacturer's specified level is set to ensure that the power steering system operates efficiently and safely. A level significantly below the recommended mark indicates a risk for reduced hydraulic pressure and can cause damage to the steering components over time, making it crucial to maintain the fluid within the acceptable range for optimal performance.

The other conditions do not equate to a failure in the same critical way. For instance, having the fluid level above the recommended level typically isn't an issue unless it might lead to overflow or foaming, and issues like breakdown in viscosity do not necessarily indicate an immediate failure in terms of the fluid level itself.