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O.K. folks,
This is long but it is the only way I can describe the problem and what we
have done to date.
Two Thursdays ago I was flying from Sporty's to Elizabethtown, Ky when I
experienced a severe oil overheating problem. I put the plane down and had
to leave it up north while I went back to work and came back down south
here to Alabama.
My 415CD (C-75, no oil cooler) runs around 180 degrees on a normal summer
day. 30 minutes into my return flight I noticed the oil temp stretching up
to 200 degrees and above. As it approached 225 degrees(my redline) I
started looking for a place to put her down before drastic things began to
happen. As I found a place to land, the oil temp reached about 250 degrees
and I heard three knocks in the engine. My A&P has convinced me this was
predetonation. I immediately throttled back on RPMs and the knocking went
away. Landed with no problems. Throughout the situation, the engine never
sputtered, ran rough, or lost oil pressure below my green line. After I
landed, I checked the oil level and had a full 4qt reading.
Last weekend, on my A&P's instructions I returned to Kentucky, got an A&P
form a nearby airport and performed the following checks.
1. Changed oil and checked screen. Found no indication of problems
on the
screen.
2. Performed compression check. Results 72/68/68/68
3. Checked spark plugs for fouling. A&P said they looked fine
4. Performed Magneto alignment check. All ok.
There is no indication that airflow was restricted that could have caused
the overheating.
In other words, we found no smoking gun. After all the checks were
complete
I took the plane for a test flight. In 15 minutes flat I was at redline
again. I put her down and now the A&P and I are scratching our heads. He
wants suggestions from owners as to what else could create this problem
before he starts pulling cylinders.
Any suggestions/advise is appreciated.
John Adams
Huntsville, Alabama
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