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Oil Temp Probe Location

Vans101

Well Known Member
Looking at the location of the oil temp probe installed in the Lycoming oil filter adapter housing it appears that the temperature readings is essentially the temp of the oil as it enters the engine...if true this does not seem to be very helpful information.

When the Vernatherm is cold a great percentage of the oil is allowed to bypass the oil cooler and therefore the oil temp probe is pretty much reading the temperature of the oil that was just sucked out of the oil pan.

Then as the oil heats up the Vernatherm begins to extend and the tip blocks off the oil cooler bypass passage and then oil is forced to go through the oil cooler and when it returns to the oil filter housing if flows past the temp probe where the temperature is measured...in other words the temp probe is reading the temp of the oil AFTER it has already been cooled off by the oil cooler.

In car engines you measure the coolant temperature as it is leaving the engine and that makes the most sense to me...because you can indicate what is happening inside the engine.

Would it make more sense to know how hot the oil is really getting by measuring the oil temp at a location before the oil cooler?

On Continental engines do they also measure the temp of the oil after it is cooled?

Any information would be greatly appreciated

Thanks
 
In car engines you measure the coolant temperature as it is leaving the engine and that makes the most sense to me...because you can indicate what is happening inside the engine.

Auto engines (water cooled anyways) rarely have oil coolers, so that is not a good comparison. There are two schools of thought. While I want to know the temp of the oil in the pan (oil temp is directly related to potential oxidation at or near the critical temp), it is more important to know the temp of the oil that is beings asked to lubricate the engine (high temps create a viscosity break down that is a greater threat) and that is registered via the lycoming location.

Larry
 
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Looking at the location of the oil temp probe installed in the Lycoming oil filter adapter housing it appears that the temperature readings is essentially the temp of the oil as it enters the engine...if true this does not seem to be very helpful information.

The measurement point in the filter adapter is intended to indicate the temperature entering the filter casing, and subsequently the engine.

The two flow paths (oil cooler and direct from sump) mix (in theory) just downstream of the vernatherm bypass hole. That mixing may be imperfect under some flow conditions, so the temperature indication may not always precisely reflect the oil temperature of all the oil as it flows into the filter...but it's close enough.

If you wish to monitor sump temperature, there are a variety of ways to install a sensor. The most universal would probably be a tee fitting at the accessory case outlet port to the oil cooler. Oil flow would be inline, sensor screwed into the stem of the tee. I don't see how it would be very useful, unless you were doing cooler comparisons or something similar. That said, I've done similar things just because I was curious...

Be aware it would not be the hottest oil in the engine. That's probably on the underside of the pistons, and out in the rocker boxes.
 
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