OIl Temperature Problem Solved

[bf92]

Before my engine rebuild oil temps were 170F cross-country and would drop to 160F during a full throttle full rpm airshow on a 100F day. Since the rebuild the temps have been close to 185 x-country and would go so high during aerobatics that I would have to take a break to cool it down. Max inlet temp is 188F and the engine adds around 50F to that before it returns to the oil tank, so inlet temp is measured as it comes out of the tank.

After much thought, and even making plans for a second cooler, I thought I would try something first: I removed the Vernatherm and replaced it with a steel ball held in place with a compression spring and capped with an AN814-12D plug to hold the spring and ball against the by-pass port. And just like that the climb-out temp that was always 185F was now 150F, cruise temp is 145F, and during high-alpha aerobatics like hammerheads and hovers, the temp never got over 170F. It was simply a very odd coincidence that the Vernatherm went bad at the same time the o/h occurred, which made me think it was something about the engine that was causing the high temps.

By the way, I paid $900 for the oil cooler including the Vernatherm, but a new Vernatherm by itself is over $650.

Danny