High oil temperatures

[swanstedt]

When my IA and I did the compression check air was coming out the open oil fill cap, as opposed to the valves, about equally for all cylinders...which I believe is normal. However, we didn't try to quantify the flow at other piston positions.

No excess oil useage noted...but as you said...I haven't been able to keep it in the air long enough to get a good check on that since April.

Scott

[blueldr]

Your oil temperature rise is so rapid that I would suspect excessive blowby.
I'd almost bet that the only cure is going to be a top overhaul.

[GAHorn]

Scott, you haven't mentioned if you've verified the accuracy of your gauge, but I suspect that it may not be off anyway...
... I don't agree with you mechanic who recommended the MMO.... that's the most likely cause of the gunked up oil filter. (MMO is a solvent, defeats/dilutes your oil, and breaks loose years of dirt and subjects your engine to greater possibility of internal harm due to circulating sludge, IMHO. I'll bet he has no approval for having recommended that to you and he will not likely sign the logbooks that he did that.)
The 225 is not excessive in the summertime, and I don't see any reason that you need a top overhaul with those compression readings. I think you should change your oil using SAE 50wt, and go enjoy your airplane and quit chasing what looks like a non-problem to me.

[swanstedt]

George,
Oil temperature gauge was the first and last thing I checked out. All readings were good.

We drained the oil/MMO after only 3 hours of run time (HOBBs) and put in staight AeroShell 100.

I wish I could reasonably keep the oil temp down to 225...or 240 for that matter. The only way I found is very short flights, on cool days, without gaining enough altitude to clear much of the local terrain, and with very reduced power settings. Leave any one of these out of the equation and forget it...the oil temp keeps climbing at a rapid pace with no sign of leveling off.

If this is how an O-300 is supposed to run...anyone interested in a low time 170A?

I think Dave may have hit it with the stuck ring tip.

I'll check back tomorrow...got to ferry the plane to another airport before it heats up here then go to Salt Lake.

[blueldr]

You said that all cylinders showed good on the leakdown check. Are you sure that the leakdown gages are properly calibrated as per TCM specifications?

[swanstedt]

Yesterday morning things seemed to turn around. Hopefully what was causing the problem freed itself. I made a reduced power climb out at about 2200 rpm but the oil temp didn't climb nearly as fast as the day before. At the point where I had reached 210 two days ago I was only sitting at about 170 and slowly climbing.

I was able to cruise climb to about 5K AGL in my 45 mile trip with the oil temperature only rising to about 215 and holding steady. Before I made my circling decent I applied full power and went into a hard climb to see what would happen at the higher manifold pressures. Oil temps climbed to about 230 with a slow creep upwards. I reached about 5500 AGL (10,750') before I reduced power to set up for landing.

No way in hell would it have let me do this even two days ago. About the only thing I did different was not apply full power until the very end of my ground run. I don't know if this happened to be the key to break things loose in my case but I'm much more optimistic that our oil temperature problem may have cured itself.

blueldr, I don't know for a fact the gauges were calibrated as per TCM specifications. I would have to assume so since my IA takes care of a commercial fleet with both Lycoming and Continentals and is pretty anal in their care. Even if it wasn't, all cylinder measurements were very consistent regardless of the calibration.

Scott

[blueldr]

I mentioned the calibration of the compression leakdown test gages only because some gage sets have an oversize orifice that allows too much airflow during the test and that will give a false reading. If the airflow is too great, the reading will be high on the engine side gage with excessive leakage past the rings into the crankcase. This will disguise likely excessive blowby during operation of the engine.

[mrpibb]

Does the 51 170's have a pressure cowl like the 48 and 49's? if not the following will be a mute point, but all this talk of high oil temps led me to re-evaluate my oil temps. I consistently run in the red during the summer months and will also in the cooler weather at the higher power settings. I run 2500 to 2550 rpm for cruise for the reason I'm running a EM pitch to 50". on a hot summer day it was not uncommon for me to run high temps at power setting down to 2350. This never bothered me for my temps would rarely never go past 225, only sometimes on long en-route climbs or slow flight. Last week I changed my oil and filter, I had the airplane nosed into the flight schools hanger which was dark, I walk to the back of the hanger to get a oil bucket, when i turned around to walk back to the airplane it was then I noticed the daylight I could see all around the inside of the pressure cowl.
I happened to have absconded that morning from work a roll of the the magical mystical roll of the adhesive backed foil tape ( known as speed tape in the Industry). I proceeded to tape all the seams and gaps in the pressure cowl. I completed the oil change but did not fly long enough to get the temps up ( to many t-storms in the area ). I did however fly today for about 1.7 hours at cruise and high cruise ( 2550 to 2650) oat at 2500ft was 70 deg F. What I had for oil temps were very encouraging It took a lot longer for my temp to come up as It used to, it would take about 15 Min's on a warm to hot day to reach 215 to 225 deg at 2550. today it never reached 225 or 215 for that matter. I did a long full power slow climb for about 15 Min's, stayed at 2600 rpm for another 15 Min's, I never got into the red. I was in the green about 2 needles width from the red. after about 30 Min's total I reduced power to about 2500 rpm and my oil temp dropped about another needle width. if I was to extrapolate I would say it was about 195 ish. I flew for another 45 mins at 2550 and my temp stayed below the red range mark. So with the tape job I would say I had dropped a respectable 20 degs in oil temp. So it looks like this annual the focus is going to be on the pressure cowl

[GAHorn]

Does the 51 170's have a pressure cowl like the 48 and 49's? if not the following will be a mute point, but all this talk of high oil temps led me to re-evaluate my oil temps. I consistently run in the red during the summer months and will also in the cooler weather at the higher power settings. I run 2500 to 2550 rpm for cruise for the reason I'm running a EM pitch to 50". on a hot summer day it was not uncommon for me to run high temps at power setting down to 2350. This never bothered me for my temps would rarely never go past 225, only sometimes on long en-route climbs or slow flight. Last week I changed my oil and filter, I had the airplane nosed into the flight schools hanger which was dark, I walk to the back of the hanger to get a oil bucket, when i turned around to walk back to the airplane it was then I noticed the daylight I could see all around the inside of the pressure cowl.
I happened to have absconded that morning from work a roll of the the magical mystical roll of the adhesive backed foil tape ( known as speed tape in the Industry). I proceeded to tape all the seams and gaps in the pressure cowl. I completed the oil change but did not fly long enough to get the temps up ( to many t-storms in the area ). I did however fly today for about 1.7 hours at cruise and high cruise ( 2550 to 2650) oat at 2500ft was 70 deg F. What I had for oil temps were very encouraging It took a lot longer for my temp to come up as It used to, it would take about 15 Min's on a warm to hot day to reach 215 to 225 deg at 2550. today it never reached 225 or 215 for that matter. I did a long full power slow climb for about 15 Min's, stayed at 2600 rpm for another 15 Min's, I never got into the red. I was in the green about 2 needles width from the red. after about 30 Min's total I reduced power to about 2500 rpm and my oil temp dropped about another needle width. if I was to extrapolate I would say it was about 195 ish. I flew for another 45 mins at 2550 and my temp stayed below the red range mark. So with the tape job I would say I had dropped a respectable 20 degs in oil temp. So it looks like this annual the focus is going to be on the pressure cowl

The "pressure cowl" term refers to the type cooling which came out on the '53 B-model and later aircraft. The earlier type cooling, which was common for all aircraft from '48 thru '52 models, was not a "pressure cowl"...it was an internal air-box type. ("Pressure cowl" means a cowling which is pressurized.)

In any case, the condition of whichever design cowling you have will affect engine cooling, both cylinders and oil.

This has been said elsewhere, but just a reminder: The early green-arc/225-degree-redline guage is not the most readable gauge in light of the later change to this engines type certificate, which allows oil temps up to 240 when using straight-weight (not mulitgrade) SAE 50 AD oil. (See this engines type certificate notes section.)

[mrpibb]

I guess the " non" part of the word didnt make it in as I ment non pressurized, sorry for that, it was late. However I did drop 20 deg after sealing things up abit, I'll take that.