Toyota received complaints about Lexus engine defect in 2007


Foreign material enters the spring?

Sounds like metallurgical impurity due to inclusions...

What I would like to know:

1. Who is the supplier of these springs, and why did that supplier fail to a) maintain purity, and b) detect the departure from the material specification ?

2. If this level of impurity is "normal" within the material specification, why did Toyota not design the spring properly in the beginning?

Finally, is this another example of Toyota's "under-estimating" the frequency and effect of a failure-mode, and/or doing a silent upgrade or repair without informing NHTSA within the 5-day statutory requirement?