An interesting thing about Lycoming engines -- the oil cooling system is mostly external to the engine.
- Power/Engine Approach: "is the engine producing too much heat?"
A. Heat is a byproduct of power so is the engine producing too much power? or have you modified it in any way to increase power (such as cold air induction, increased compression, piston oil squirts, extra cylinder fin insulation (thick paint), etc.). If so, then cooling system might not be sufficient for heat loading.
B. Is the engine fuel consumption in agreement with charts? (another check on power output and if the mixture is too lean)?
C. Is the oil being heated by combustion gas blowing past the piston rings? Go to step 2
- Cooling System Approach: Is there adequate oil flow through the cooler? Is the bypass valve working properly? Go to step 3
- Not an engine problem but an airframe problem.