Rotax has issued Mandatory Service Bulletin ASB-2026-002 for 915 iS and 916 iS engines. The problem has to do with cracks in the engine’s turbocharger valve housing (Rotax part number 956492) that left unchecked can result in oil leakage out the turbo and onto hot exhaust components.
Rotax (noting a manufacturing defect from the supplier) discovered the problem during end-of-line testing, and further investigation found cracks and insufficient wall thickness on the affected housing assemblies. The bulletin calls for immediate exchange of the valve housing before the next flight and of course before installing a new engine or component. It’s pretty straightforward as the image from the service bulletin shows: the turbocharger valve assembly and a sealing ring. Some disassembly is required.
Remove the banjo bolt from the turbo pressure oil line at the oil pump housing, remove a couple of Allen screws, lock nuts, and cable clamps, remove the turbo pressure oil line, and then the valve. Reinstall proper replacements and leak check it.
The bulletin says the replacement kit is provided at no charge and labor credit will be provided for the work that’s performed by a technician with current applicable iRMT rating.
That’s the way to handle a service bulletin. Many of the “legacy” GA engine manufacturers should take note. Maybe that’s why they’re legacy?