Nice big hole in the weather over Corona and Chino.
I finished the flight up with some pattern work, since that usually cranks the oil temp right up. Even so, I couldn't get the oil temp over about 192 no matter what I threw at it. Usually as I'm taxiing back in it cranks up a bit, but today it was just too chilly for it to get very high. Good enough, though. I popped the cowl off and drained the oil. As it drained I did my usual inspection. This is something I saw as soon as the bottom cowl came off...the retainer ring on the one-hole eyeball for the throttle cable had come loose.
Fortunately the ball halves hadn't moved...they would have been strewn about the central valley if they had. Anyway, I just replaced the ring and used threadlock on it this time.
When I originally installed them, I used some torque seal so I could watch for any loosening. The other three out of four eyeballs look fine. I'll definitely keep an eye on this, though.
Oh...what's this?! Poking my head around I noticed some cracking on the inboard oil cooler flange.
Yep, that's comin' off.
The soft flange on the oil cooler cracked in three places.
The baffles are totally fine...but now that they're rock solid, the oil cooler is taking the brunt of the vibration. And the way I fastened it to the oil cooler -- per plans, is just plain DUMB. It's my own ignorance. Total 20:20 hindsight here.
Now this is what is totally, absolutely ignorant (on my part). And this is per plans (unless I've missed something). You've got these lengths of aluminum tubing, acting as a sleeve on the bolt, which sits between the two flanges of the oil cooler. The tubing keeps the flange from bending inward as you tighten the bolt. All well and good, but there is simply NOT enough surface area where the tubing contacts the flange. Jeez, how could I miss this? How could the plans not call for a large washer in there? All you gotta do is put a "large area" washer (trimmed if necessary to fit) between the flange and the tubing, and this wouldn't have happened. I'll bet even a simple AN960-10 or -10L would have alleviated this problem.
And to think this is the GOOD side. And somebody please tell me why I only used four bolts, not all six?! Oh yeah, the plans that I blindly followed. Think about it...if I had used all six bolts, that theoretically would have been 50% less stress on each fastener. Dag bernit. Crystal clear, looking at it from this perspective, 250 to 300 hours into the life of this oil cooler.
Seriously. Any expert would have seen this coming a mile away. And now of course you can't miss it.
I gotta see if Pacific Oil Cooler can repair this. I remember my hangar neighbor had the same thing happen on his Cessna, and he said he was able to have it repaired. We'll see what Pacific says in the morning.
So...to summarize, here's what I'm going to do differently:
I'm extremely happy that my baffles and brace design have proven themselves worthy, but obviously the weakest link is now these very soft, susceptible oil cooler flanges. Easy to address with this hindsight. You had better believe there will be some photos coming of the faulty drawing and of the "fix."