Monday, June 11, 2012

High oil temperature on Lycoming aircraft engine

I don't have a canned solution except to suggest a process:

An interesting thing about Lycoming engines -- the oil cooling system is mostly external to the engine.

  1. 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
  2. Cooling System Approach: Is there adequate oil flow through the cooler? Is the bypass valve working properly? Go to step 3
  3. Not an engine problem but an airframe problem. 


  1. I've had the vernatherm valve on an IO-540 not close when the oil system pressure was set too high (too many washers under the pressure relief spring).

  2. What if changing the aircraft engine, that engine is warming up in the other plane?

  3. Engine baffling bent backward or not sealing is the first and easiest item to check.

  4. ¿Installing the engine on another plane?
    Not heated above.

    sorry, I use Google translator. Thank you.

  5. Other engines installed without baffles or in poor condition they are not heated.
    Thanks John