Oil temp

simatos · Post by **simatos** » Fri May 20, 2005 8:00 pm

I cranked up my engine for the first time and anxiously watched all the gauges. Pressure EGT and CHT all came up fine. I didn't run the engine long perhaps 2 minutes mabe a little longer but got no movement on the oil temp gauge. It is one of the infamous SCOTT gauges. I must admit the actual oil pan didn't feel particularly hot. Till I have the cowls sealed nicely i am a little fearful to runn the enging longer but how long would you expect before the oil temp begins to register a rise Thanks G

N170BP · Post by **N170BP** » Fri May 20, 2005 8:02 pm

Mine (also a Scott) won't hardly move on the ground
no matter how long you run it (at least with the relatively
cool temps we have in the Pacific Northwest).

I have to go fly it and climb/cruise for a few minutes
for the oil temp to start registering.

cessna170bdriver · Post by **cessna170bdriver** » Fri May 20, 2005 9:05 pm

The bottom of the scale on the original Scott gauge is 100 deg F. Even on an 80 degree day, mine takes several minutes (5-10) to come off of the stop, and a few minutes more at 1000-1200 RPM to get to the 100 degree mark.

I know the owner's manual says that you don't need an oil temperature indication to take off, just a smoothly accelerating engine, but I've made it a habit to wait to do the run up until the oil temp reaches 100.

If you doubt whether the oil temperature gauge is working, immerse the probe in boiling water (be careful about how you do that around your airplane!) while someone is watching the gauge.

Miles

zero.one.victor · Post by **zero.one.victor** » Sat May 21, 2005 12:18 am

I think it's a good idea to check the temp probe in boiling water- remember that water boils at 212 degrees at sea level. That's not too far from where most C-145/O-300's oil temps are at, at least in warm weather, so you'll then have a pretty good idea of what your actual oil temp is compared to what the gauge is reading.
A friend installed an OH'd gauge in his Clipper recently, he told me that he checked the gauge by dunking the probe in a cup of hot (not boiling) water which he heated up using the microwave in his hangar ("the needle moved!"). I told him that in my opinion he didn't test or prove a darn thing except that the gauge's needle isn't frozen. He was too lazy or impatient to take the gauge back home & test it properly. It's so easy to do when the gauge is out anyway that I think it's almost criminal not to.

Eric

simatos · Post by **simatos** » Sat May 21, 2005 4:48 am

Guys thanks Your info is reassuring, I think I will do the boiling water test on the stove at home cheers g

zero.one.victor · Post by **zero.one.victor** » Sat May 21, 2005 5:06 am

FWIW I've tested two of the "infamous" Scott oil temp gauges when new, they both read just about 205-ish when the bulb was immersed in still-boiling water. Close enough for my purposes.

Eric

Steve Jank · Post by **Steve Jank** » Sat May 21, 2005 11:21 am

Okay, my gauge reads approx. 20 degs. high...Since comments made in replies indicate change....What brand of oil temp. indicator should be
installed???

Post by **GAHorn** » Sat May 21, 2005 7:44 pm

Scott is a good brand, as is Rochester. Both sold by Spruce.
Remember,...when checking in boiling water do NOT allow the probe to touch the sides of the pan or it'll read erroneously high.

Roesbery · Post by **Roesbery** » Sat May 21, 2005 9:06 pm

Also don't forget that water boils at 212 degrees F only at sea level on a standard pressure day. Higher pressure higher temp, lower pressure lower temp. Boiling water can and will freeze if the pressure is lowered enough. Some cook books will give a rough breakdown for boiling temperatures at different altitudes.

N2865C · Post by **N2865C** » Sat May 21, 2005 10:34 pm

John's Great Oil Temp Adventure.
I'm working on my oil temp as well. This is what I have learned so far......
I have an original oil temp gauge that redlines at 225, but there is lots of room on the dial after the line. Knowing that I bump up against redline sometimes during hot weather, and knowing that O-300 is certified to 240 with 100 wt., I decided to mark my gauge at 240. Seemed like a good idea at the time. I learned a couple of things in the process.

I removed the probe, heated some oil to 280, removed the oil from the heat and put the probe in the hot oil. Then I checked the oil temp against a thermometer in the oil and I waited for the oil temp gauge to rise and then fall back to 240. Much to my surprise the gauge never went beyond 225 after several attempts. The gauge is marked something like " operating range 100 to 225". I should have taken the hint. I think I cooked my gauge. My gauge is now reading what I am guessing is about 10 degrees hotter than it was before I started, so I guess I'll order a Scott and try that.

The other thing I learned is that there is a lot of lead and lag time with the gauge. It was taking a couple of minutes for the gauge to catch up (or down) with the oil temp. So, if you are marking your gauge you need to keep the oil (or water) at a constant temperature.
jc

zero.one.victor · Post by **zero.one.victor** » Sun May 22, 2005 5:05 am

Roesbery wrote:........Boiling water can and will freeze if the pressure is lowered enough..............

While this may be scientifically correct, this sounds like the punchline from one of those stories that you will only hear from Texans or Alaskans!
You know, like "it was so cold that the campfire froze....."

Eric

Post by **GAHorn** » Sun May 22, 2005 11:07 pm

N2865C wrote:John's Great Oil Temp Adventure.
I'm working on my oil temp as well. This is what I have learned so far......
I have an original oil temp gauge that redlines at 225, but there is lots of room on the dial after the line. Knowing that I bump up against redline sometimes during hot weather, and knowing that O-300 is certified to 240 with 100 wt., I decided to mark my gauge at 240. Seemed like a good idea at the time. I learned a couple of things in the process.

I removed the probe, heated some oil to 280, removed the oil from the heat and put the probe in the hot oil. Then I checked the oil temp against a thermometer in the oil and I waited for the oil temp gauge to rise and then fall back to 240. Much to my surprise the gauge never went beyond 225 after several attempts. The gauge is marked something like " operating range 100 to 225". I should have taken the hint. I think I cooked my gauge. My gauge is now reading what I am guessing is about 10 degrees hotter than it was before I started, so I guess I'll order a Scott and try that.

The other thing I learned is that there is a lot of lead and lag time with the gauge. It was taking a couple of minutes for the gauge to catch up (or down) with the oil temp. So, if you are marking your gauge you need to keep the oil (or water) at a constant temperature.
jc

How did you determine that the oil you heated was to 280? How can you be certain that the method was accurate? How can you be certain that the act of plunging the probe into the oil did not lower the oil temp considerably? (And finally, heating engine oil on an open flame or stove-top can be dangerous due to flash-over. Cooking oil is better for the purpose. Be careful out there.)

N2865C · Post by **N2865C** » Mon May 23, 2005 2:51 am

How did you determine that the oil you heated was to 280?
I had an instant reading digital thermometer with a range of 0 - 350 f. I checked it in boiling water, it was very close to 212 (off by a few degrees, 160' msl about 65 degrees outside)

How can you be certain that the method was accurate? How can you be certain that the act of plunging the probe into the oil did not lower the oil temp considerably?
The thermometer was in the oil for the entire process. I heated about a quart of oil. Even if the act of plunging the probe into the oil did lower the temp, it would have shown up on the thermometer.

And finally, heating engine oil on an open flame or stove-top can be dangerous due to flash-over.

I heated the oil in a heavy pot on an electric burner outside my hanger with a fire extinguisher near by, repeating over and over to myself "I wonder what the flash point of oil is???" I figured 280 was safe. Carrying the oil back into the hanger I kept thinking about those old movies with the Romans pouring boiling oil on the invaders. I was very careful.

Cooking oil is better for the purpose. Be careful out there.)
The cooking oil is a great idea, very good advice. I could have had French fries when I finished!!

jc

Post by **GAHorn** » Mon May 23, 2005 5:33 am

Ahhh. Excellent! (But wasn't it the Greeks who did the hot oil thing on enemies?)

Jr.CubBuilder · Post by **Jr.CubBuilder** » Mon May 23, 2005 3:53 pm

My Scott gauge quit working, after I had been unable to fly for three weeks. I'm hoping the needle is just frozen, any suggestions besides the boiling liquid? I've still got a few hours before an oil change is due so I would prefer not to pull the probe out till then if I can get away with it.

The International Cessna 170 Association

Oil temp

Oil temp

Scott oil temp. gauge?