Cylinder softness
Hello,
My brand-new airplane with a Rotax 912iS developed a coolant leak at just 42 hours due to a clamp that was not properly torqued. As a result, the coolant temperature exceeded 270°F for about 10 minutes, after which no further record was logged in the G3X.
The AP sent the cylinder heads to a Rotax dealer, where the harness test results came back as follows:
- Cylinder #1: 148.2
- Cylinder #2: 112.9
- Cylinder #3: 115.4
- Cylinder #4: 114.6
With the cutoff being 85, all cylinders remain within limits. However, cylinder #1—which is normally the coolest—registered the highest value, indicating that the overheating softened the other cylinders to some extent.
While the results technically pass, I remain concerned about long-term reliability and potential future issues. It’s particularly disappointing since the coolant leak was caused by improper assembly rather than anything on my part.
What do you suggest I do in this situation? Does anyone know the typical hardness values for a brand-new cylinder head? I feel this issue has already devalued my brand-new airplane significantly, and it has now been grounded for over a month.
Thanks!

