Cessna Oil Temperature

[LesGawlik]

I flew with a friend today in his new P Ponk 182. The oil temp never got above 111* in an hour plus of flying, according to his JPI 830. My 182 O 470 R never moved the needle more than a needle width off of cold on the standard gauge. I thought the gauge was broken, but now I suspect it was correct. Both engines have the oil cooler in the starboard side in the front of the cowl.

I really don't understand what's going on. Let's start with the engine oil at ambient, say 40*. the engine starts, and begins making heat. The vernatherm should be closed, stopping oil flow to the oil cooler. Shouldn't this closed circuit system remain until the oil reaches the temperature at which the vernatherm operates? Assuming that the vernatherm is not stuck open.

If that's the case, then putting aluminum tape over the oil cooler should not make a difference in cooling the oil. (It would block the airflow which normally passes though the oil cooler and passes over the engine.) The vernatherm would not be open because the oil in the sump never got to the temperature necessary to open it.

I can't think that oil temps below 180* can be good for engine longevity. A lot of the moisture likely remains in the crankcase. CHTs were low, and EGTs were WNL.

 

[Randomskylane]

I flew a 182 last week with oat at 0 Fahrenheit and oil was 156 on the JPI 830 fwiw. Cowl closed obviously, carb O470-R full at 12 quarts

 

[Stewartb]

Tape the cooler. Mine’s taped at 50% in summer, at least 75% in winter.

 

[John Pringle]

I have a 182 with two year old Pponk and it regularly runs as displayed on my jpi930 in the 170 to 180 down here in So California 111 is really cold seams not warm enough to rid itself of any moisture from condensation

 

[Gary Ward]

I flew with a friend today in his new P Ponk 182. The oil temp never got above 111* in an hour plus of flying, according to his JPI 830. My 182 O 470 R never moved the needle more than a needle width off of cold on the standard gauge. I thought the gauge was broken, but now I suspect it was correct. Both engines have the oil cooler in the starboard side in the front of the cowl.

I really don't understand what's going on. Let's start with the engine oil at ambient, say 40*. the engine starts, and begins making heat. The vernatherm should be closed, stopping oil flow to the oil cooler. Shouldn't this closed circuit system remain until the oil reaches the temperature at which the vernatherm operates? Assuming that the vernatherm is not stuck open.

If that's the case, then putting aluminum tape over the oil cooler should not make a difference in cooling the oil. (It would block the airflow which normally passes though the oil cooler and passes over the engine.) The vernatherm would not be open because the oil in the sump never got to the temperature necessary to open it.

I can't think that oil temps below 180* can be good for engine longevity. A lot of the moisture likely remains in the crankcase. CHTs were low, and EGTs were WNL.

I installed these yesterday to help with oil temps. I haven't flown with them yet to see if any difference. In my way of thinking if you tape off the oil cooler then more air get's forced down through the motor?

Painted them for now with propeller paint.

Held in place by camloc fastners.

 

[sourdough44]

I flew a few days ago, ground temp 15 degrees. My oil temp stabilized at 175 or so. Yes I use a blocker of sorts, different engine.

With most any engine, there are ways to restrict airflow to the oil cooler.

 

[CT583]

My 182 also does this. It’s a little alarming to see oil at 110 degrees. Just globs of viscous liquids trying to cool down the engine.

I noticed on the next flight after one of these cool oil events, the dipstick had oily condensation spots all the way up to the handle.
They almost looked like rust, but I refused to believe that.

 

[LesGawlik]

I installed these yesterday to help with oil temps. I haven't flown with them yet to see if any difference. In my way of thinking if you tape off the oil cooler then more air get's forced down through the motor?

Painted them for now with propeller paint.

Held in place by camloc fastners.

Where did you get those?

 

[Plano Pilot]

Bad or missing Vernatherm? I had one go bad on a 520 and oil temp started running warmer than normal. Maybe yours failed the other way or not installed?

"Oil can also bypass the oil cooler if the vernatherm valve is defective. The vernatherm is just like the thermostat on your car’s radiator. It’s a temperature-sensitive valve that regulates oil temperature by controlling oil flow through the cooler. As a rule, it strives to keep oil temp at around 170 degrees F. You can check the vernatherm’s basic operation the same way you would a car’s thermostat. Just drop it in boiling water and it should open wide. That’s nice, but it really doesn’t tell you what you need to know. Be scientific and methodical about this: Get a good, accurate thermometer (or temperature probe on a multimeter) and put it and the vernatherm in a pan of cold water. Start heating the water. (Some mechanics insist that water is not as accurate as oil, and use oil instead, but it’s a messier proposition.) Continental vernatherms, for example, should open when the water temperature gets up to 180 or 190 degrees. If it doesn’t, chuck it and get a new one. A Continental vernatherm marked 77 C should travel at least 0.090 inches as the water temperature climbs from 120 degrees up to 170 degrees. Those marked 173 degrees should travel at least 0.16 inch as water temperature rises from 135 to 173 degrees."

From: Oil Temperature Control Systems (avweb.com)

 

[LesGawlik]

My understanding of engine cooling is that airflow must be directed over the top of the cylinders, across the cylinder fins and then exited on the bottom side of the cowl by the firewall. So anything that impedes the flow of air into the engine will decrease engine cooling.

But masking off the oil cooler should have no direct effect on the oil temperature, correct? Oil will not be flowing through the cooler until the engine temperature reaches the necessary temperature to open the vernatherm, assuming it is functioning properly, correct?

 

[Stewartb]

In Alaska, I rarely see anyone use a winter front. I had a winter front kit for 25 years. Used it for about a half hour before landing to remove it as CHTs got warmer than I liked. Duct tape on oil coolers is standard practice. The picture shows my summer coverage. I cover more in winter.

 

[Wagondriver]

It might make a difference in where you are picking up the temperature. My 520 has the factory mechanical pickup in the case below the oil cooler, that temperature is oil before it goes through the cooler. My JPI830 sensor is on top of the engine just inboard from the cooler. That, I believe, is oil temp after the cooler.
In the winter, my preheater has the entire engine at about 94 degrees. After a few minutes of running it will be reading in the low to mid 40's according to the 830. Meanwhile the factory gauge is going up into the normal operating range. After a few minutes of flight you can watch the numbers climb on the 830. Normal temperature on mine in the winter is almost the same as in the summer, about 183 degrees. However, after a long low power descent, oil temp after the cooler will drop down to 110 or so. I assume that means that in that long descent the vernatherm closed and oil stopped going through the cooler.

I have flown with ground temps in the minus 10 or so range many times, usually a couple thousand feet up it is in the 20's or even warmer. I have found no need to close off my oil cooler.

 

[Domenick]

I do not believe a vernatherm can stop oil flow. There is always a bypass.

 

[Clip4]

I do not believe a vernatherm can stop oil flow. There is always a bypass.

Vernatherms are are like thermostats in cars. If a small amount of fluid is leaking through the engine will not get to the desired temperature.

 

[Stewartb]

Huh? The temp valve on a Cessna diverts flow to the cooler when engine oil gets to temp. If you ground run long enough you can see it on the temp gauge at about 130* when the temp drops. If the valve isn't working the oil will run hot. With a non-congealing cooler there's always some oil flowing to the cooler, but that has nothing to do with the temp valve.

 

[Clip4]

Huh? The temp valve on a Cessna diverts flow to the cooler when engine oil gets to temp. If you ground run long enough you can see it on the temp gauge at about 130* when the temp drops. If the valve isn't working the oil will run hot. With a non-congealing cooler there's always some oil flowing to the cooler, but that has nothing to do with the temp valve.

If the valve is partially stuck open then?

 

[Jon Wilder]

If the valve is partially stuck open then?

The Vernatherm controls a bypass path. When it heats up, it expands and blocks the bypass path, thereby diverting oil through the cooler. However, when it's below its spec'ed temperature, it shrinks, thereby opening a bypass path around the cooler. Oil then bypasses the cooler and stays in the engine longer, allowing it to heat up to the Vernatherm's operating temperature, before closing the bypass path again and forcing oil to divert to the cooler.

If the Vernatherm is stuck partly open, or it isn't properly seating and closing off the bypass path 100%, you will have some leakage around the cooler, thus the oil temps will be hotter than normal.