I would like to share a problem I have been experiencing recently with the engine temperature during descent to the airfield in my Saratoga II TC aircraft, equipped with the TIO 540 engine.

The situation is as follows: During ascent and cruise, the engine oil temperature remains stable at 190 degrees, which is within the normal parameters for our TIO 540 engine. However, when I commence the descent to the airfield, the temperature starts to rise and can reach up to 250 degrees. What concerns me most is that this does not happen on every flight, making the issue even more perplexing.

I have already checked the temperature sensor, which appears to be functioning correctly. However, I suspect that the problem is not a simple misreading of the sensor, as the oil pressure also drops when the temperature rises, indicating that there is something going on with the cooling system.

It is worth noting that the thermostat valve was replaced less than 100 flight hours ago, and during the first 50 hours after the replacement, the problem did not manifest itself.

If anyone has encountered a similar issue with a TIO 540 engine or has any ideas about what could be causing this sudden increase in temperature during descent, I would greatly appreciate any guidance or advice you can provide.

Is the type of oil being used appropriate for the OATs?

More of a winter time issue, but I have seen for example 100 straight weight oil used, or even 80 and very cold temperatures, the oil can congeal in the cooler and not allow oil to circulate through the cooler, then the oil temp will go up and up because it can't be cooled.

I know you probably checked this, but how are your baffles?

PilotPeat wrote:Is the type of oil being used appropriate for the OATs?

More of a winter time issue, but I have seen for example 100 straight weight oil used, or even 80 and very cold temperatures, the oil can congeal in the cooler and not allow oil to circulate through the cooler, then the oil temp will go up and up because it can't be cooled.

I'm currently using W100 oil, for an average ground operating temperature of 70 degrees. I will check in the engine operating manual for the proper oil

NineThreeKilo wrote:I know you probably checked this, but how are your baffles?

All brand new

Did you ever figure out what was going on here. Having a similar/exact same issue. One piece of interesting information is I had to descend because of icing as I had just gone into negative temperatures for the first time since owning this plane. It remained an issue into the next flight and then fixed itself magically on the next flight, mid-flight as OAT started to rise above freezing, oil temp rapidly came back to normal, and when I started my descent it started creeping up again. Seems like we are having something similar going on and I am scratching my head here. I'd love to hear if you have made progress here.

Just wanted to follow up and see if you'd figured out what was causing this. Having the same issues.

From what I understand its possible that the Oil Coolers themselves get somewhat clogged with Carbon due to the turbo and can restrict flow when oil temps get cool and oil thickens.