SonexBuilders.net

Hello,

I have the Aerovee engine with a top mounted oil cooler installed in a Sonex Onex. I updated the baffle system I/A/W Sonex recommendation. However: I continue to expierence high oil temperatures during climb out and cruise. I live in central Florida and the temperature in the summer is usually in the low 90 degrees Fahrenheit range. The oil temperature approaches 230 degrees during most operation. At that point I have to reduce power to get the temps back down. I have removed and cleaned the oil cooler. Still no help. Any ideals out there?
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CPT Tidy

How many hours on the engine? Where is your oil temperature probe? In the sump? How is the oil pressure when the temps are displaying high? Is it a digital readout or a steam gauge?

Even with the top mounted cooler, Sonex still recommends (or they used to) getting air to flow through the cowl and under the oil sump.

I moved my cooler from bottom to top, but I left the smiley opening from the bottom mounted cooler setup. In the winter I have a plate to fully block the opening (it gets cold in the winter in Massachusetts). In the summer I either partially block the opening, or open it up fully to get air under the sump. I have never had any oil temperature issues.

There was a spirited conversation about this a while back, wondering if the lower oil temperature was because the probe was getting cool air, but the oil wasn't, really. I don't know the answer for sure, but I know that flying in 95 deg temps up here, and to and from OSH several times, I've never had any oil issues.

Hi CPT,

You are correct, 230F is extreme for an AeroVee. When I fly in 90 degree weather, which is rare, my oil temperature in my OneX will top out at around 160F. I have the top mounted cooler.

Mike Smith asks a good question: where is your probe located? Mine is in the blockoff plate on the left (from pilots prospective) front of the engine. The other popular mounting location is on the oil sump plate.

What are you using for your oil temp gauge. Some digital gauges need to be configured to match the type of probe.

About 160F with a bottom mounted cooler and I enlarged the "smile" to get temps under control. In the winter I baffle the smile so the oil will actually warm up.

Great ideals all. I will check out your recommendations and get back with you.
Thanks all,
CPT Tidy

Hi I have enclosed a PDF of the oil temperature probe. Oil pressure remain normal throughout the flight. I have a EIS 4000 electronic engine monitoring system.

Thanks,

Jerry

What is your oil pressure doing? If the oil temp is really getting hot then the oil pressure will get lower.

Cpt.tidy wrote:Hi I have enclosed a PDF of the oil temperature probe. Oil pressure remain normal throughout the flight. I have a EIS 4000 electronic engine monitoring system.

One more question: do you have a "smiley" opening in the front of the lower cowl (to let in air across the bottom of the sump)? I think the probe is in a good location to not be affected by air coming in the smiley. If you don't have a smiley then you may need to be willing to experiment by adding one. Since I used to have a bottom mounted cooler, I left the lower oil cooler baffling in place to help channel the air under the sump.

No lower intake. I may have to consider adding one.
Thanks all,
CPT.TIDY

Cpt.tidy wrote:No lower intake. I may have to consider adding one.
Thanks all,
CPT.TIDY

Before you cut into the cowling ...

There are two possiblilities:
1) Your oil is 230F and your gauge says 230F
2) Your oil is 150F and your gauge says 230F

If you're positive the probe and gauge are correct then correct the oil temp problem. If not eliminate the possibility of an instrument reading failure first. It might be a bit messy but one possibility is to dunk the probe in boiling water.