What's new
Van's Air Force

Don't miss anything! Register now for full access to the definitive RV support community.

Erratic CHT on Cylinder 2 Lycoming 390

design4p

Active Member
Hello,

Now 43 hours from new - last flight the CHT on Cylinder 2 of my Lycoming 390 performed erratically whilst the other 3 CHT were as normal at around 340 Fahrenheit (170 degrees C). Number 2 cylinder moved very quickly between 340 and 410 Fahrenheit (170 and 210 degrees C) and then returning back to normal.

I tried various settings flying LOP and full rich but the erratic CHT on cylinder 2 continued.

Any suggestions of the cause would be most welcome.

John
 
Number 2 cylinder moved very quickly between 340 and 410 Fahrenheit (170 and 210 degrees C) and then returning back to normal.

The cylinder has thermal mass, so "very quickly" suggests an instrumentation issue. How quick was it?
 
Quickly is relative - if it was a matter of seconds, that's instrumentation. If it was a matter of minutes, then it has a possibility of being real.
 
If the engine feels the same as before the erratic readings, I agree with Dan and it is most likely an instrument problem. I would trouble shoot in the following sequence. Check the egt probe connections. Replace the crimps. Check the probe. Replace the probe. Somewhere in the sequence I would check where the wire connects to the engine monitor. With only 40 hours, my best guess would be an electrical connection issue.
 
Hi,

Thanks for the replies - All good information - I will check as suggested.

Great support this Vansairforce forum.

John
 
EGT

If EGT was stable on all cylinders during the event, chances are that it is a
poor crimp or a bad probe.
CHT is slower to react than the EGT if something happens.

Good luck
 
Back
Top