High Oil Temp readings that aren't accurate.
(Moved from another thread.)
On many flights, my Oil Temp readings are rock solid in the 187F range, pretty much unwavering. But sometimes oil temp readings will rapidly climb up into the 230-240 or higher ranges. I might cruise along for 2 hours with oil temp at 187, and then the temps climb up with no apparent trigger. When this happens, CHT and EGT readings are still very good. CHT's are typically 330-350 in cruise even when this happens. I've never seen Oil Temp come back down in flight once this happens, but I can stop the airplane and immediately restart and the readings are OK again. I've already replaced my vernatherm and oil temp probe, and this problem persists.
- When this happens, there is no effect on Oil Temp with changes in power or mixture settings.
- Disabling ALT, in flight, causes oil temp to immediately drop back to normal temp.
- After shutdown, the temp reading also drops immediately into the normal range.
Last advice from AFS:
- check engine ground.
My engine ground looks good. It's a heavy gauge wire (4AWG), and solidly connected to both engine and primary ground point on firewall. I did notice, however, that the wire grounding my panel was loose. The nut holding the panel ground terminal to the primary ground post had backed off, and although the ground wire terminal was still on the post, it would definitely have been a weak ground for the panel. Before next flight, the nut will be tightened back down with locktight (or with a nylock nut). I'll update the forum if the problem doesn't recur in the next several flights.
- I also noticed there is mention of going with a 2-wire oil temp probe in some older posts. I am considering this. If I install one of these 2-wire sensors, do I run one of the two leads to the oil temp input and the other to case ground?
Last edited by dhall_polo; 11-29-2010 at 10:39 AM.