Hi Steve, thank you for another detailed explanation; I know you have done a great deal of instrumentation on these engines and I appreciate your feedback – those plots are priceless.

My oil temperature probe is mounted at the return port after the second oil cooler; my coolant temperature probe is mounted near the water pump outlet.  The Mazda oil cooler was NOT installed when the hose failed.

So from your explanation, the Mazda oil cooler is not the best choice for aviation use whether it’s a single cooler or linked in series?

It would not take too much effort (2-3 hours) for me to remove the Mazda cooler and reinstall my second Fluidyne where it was previously mounted; I kept the cowl openings the same and adapted the Mazda oil cooler install to fit.  I would have to go back to installing cover plates for winter operations to control oil temperature – I can live with that and with synthetic oil, cool oil is not a huge issue.

When I get the coolant temperature under control, time to re-experiment with only one oil cooler – two is definitely overkill for winter operations.

Jeff