Oil over-temp

[Bill Boyd]

Wife and I started a cross-country to the beach yesterday and we weren’t 15 minutes out when we got an oil temp alarm for 240F. I was in fast cruise-climb and still full rich, with normal CHT’s at the time. I noted the air control knob was sitting slightly back from the full open position. Pushing and holding it in the fully-open position did not alter the trend. I throttled back, trimmed nose down and tried more like 50 fpm but the temp climb continued. When it hit 250F I pulled power and descended to a nearby airport, abandoned on a Sunday morning, and proceeded to pull the upper cowl while things cooled off.

The dipstick read just over 5 quarts, and I normally keep it at 6, so in went the spare quart from the tool kit. No air path obstruction was seen looking down the SCAT and into the cooler mount. I did note the butterfly was cocked a bit from the full open position. Tinkering with the Bowden cable a bit, it looked as if fully open was when the panel knob was about 1/2” out from the panel, so I tried to tape it in that position with electrical tape on the knob shaft. Buttoned things back up and took off, noted Oil T at 170F.

In climb, temp rose slowly as expected and stabilized at about 213-215, which is typical for it. The knob kept creeping out from the panel and I kept shoving it back in to the tape “stop.” Temp would modulate to 220 and back down again each time this happened. We flew the rest of the trip with no issues.

I find it hard to believe that adding a quart of oil made the difference (I always top it at 6qts and add one at 5), and also hard to believe that a slight canting of the butterfly air valve, which was clearly happening, would make the temps exceed redline. In all prior flights and testing, the oil cooler air flow butterfly position has made only about 15 degrees max difference in oil temps - so ineffective that I was considering removing it altogether and possibly just installing a fixed restriction for cold season flying.

Overall, I have been okay with cruise oil temps in the 200-215 range but know they could be better, so I’ve been thinking about adding a bell mouth trumpet to the air intake on the rear baffle over #6. I could also afford to direct some upper cowl airflow away from #4 back to #6 and the oil cooler intake if there is an accepted way to do this. My CHT’s in cruise yesterday were showing #4 about 20F cooler than 2 and 6…

I’m open to suggestions as to cause and cure. I can check the temp sender accuracy in boiling water when I get home in a few days.

Photo is the EFIS in cruise on the second leg after I figured out how to tweak the butterfly for max air flow. #4 is clearly getting more cooling than it needs.

 

[edhunter]

IO-320 on a RV9A. I dropped my oil level to 6 quarts after reading the lycoming didn't really need more than that, had been using 8. Flew it on a relatively cool day in March, oil temps higher than normal. Topped it off to 8 quarts, went flying a couple days later - oil temps normal. I don't lose oil flying at 8, so I now keep it at 8. I guess every engine is different... Just my experience.

 

[lr172]

Wife and I started a cross-country to the beach yesterday and we weren’t 15 minutes out when we got an oil temp alarm for 240F. I was in fast cruise-climb and still full rich, with normal CHT’s at the time. I noted the air control knob was sitting slightly back from the full open position. Pushing and holding it in the fully-open position did not alter the trend. I throttled back, trimmed nose down and tried more like 50 fpm but the temp climb continued. When it hit 250F I pulled power and descended to a nearby airport, abandoned on a Sunday morning, and proceeded to pull the upper cowl while things cooled off.

The dipstick read just over 5 quarts, and I normally keep it at 6, so in went the spare quart from the tool kit. No air path obstruction was seen looking down the SCAT and into the cooler mount. I did note the butterfly was cocked a bit from the full open position. Tinkering with the Bowden cable a bit, it looked as if fully open was when the panel knob was about 1/2” out from the panel, so I tried to tape it in that position with electrical tape on the knob shaft. Buttoned things back up and took off, noted Oil T at 170F.

In climb, temp rose slowly as expected and stabilized at about 213-215, which is typical for it. The knob kept creeping out from the panel and I kept shoving it back in to the tape “stop.” Temp would modulate to 220 and back down again each time this happened. We flew the rest of the trip with no issues.

I find it hard to believe that adding a quart of oil made the difference (I always top it at 6qts and add one at 5), and also hard to believe that a slight canting of the butterfly air valve, which was clearly happening, would make the temps exceed redline. In all prior flights and testing, the oil cooler air flow butterfly position has made only about 15 degrees max difference in oil temps - so ineffective that I was considering removing it altogether and possibly just installing a fixed restriction for cold season flying.

Overall, I have been okay with cruise oil temps in the 200-215 range but know they could be better, so I’ve been thinking about adding a bell mouth trumpet to the air intake on the rear baffle over #6. I could also afford to direct some upper cowl airflow away from #4 back to #6 and the oil cooler intake if there is an accepted way to do this. My CHT’s in cruise yesterday were showing #4 about 20F cooler than 2 and 6…

I’m open to suggestions as to cause and cure. I can check the temp sender accuracy in boiling water when I get home in a few days.

Photo is the EFIS in cruise on the second leg after I figured out how to tweak the butterfly for max air flow. #4 is clearly getting more cooling than it needs.

I seriously doubt that an extra qt of oil drops temps more than 10 degrees. Most logical guess is that cooling airflow was way down and your butterfly was closed WAY more than you thought it was. I have avoided installing one for reasons like this. I would rather fly around some days with oil at 160 to avoid what happened to you. I will run as low as 4.5 qts on my 10 and have never noticed any higher oil temps than when it has 6 quarts. I am reading capacity level temps (i.e. above VT temps) during the later parts of my climb, so would see the effect there if it existed.

Larry

 

[kiwipete]

Bill

5 quarts sounds low for a 540. I normally run mine around 9. Max is 12.

regards Peter

 

[Bill Boyd]

To be honest, I don't recall exactly what the available oil temp delta from manipulating the air control butterfly in cruise was; it's been awhile since I tested that. I may have been recalling more of the disappointing results from opening and closing the Anti-Splat cowl flap and observing the effect on CHT's. I didn't even think to try the cowl flap when the EFIS started squawking a high oil temp alarm - my focus was on where to land if it didn't stop increasing. My -10 does not currently have any gills in the lower cowl, figuring I could always retrofit one or both later if needed. The gills might aid airflow through the oil cooler if they drop lower cowl pressure significantly. I do intend to block off at least some flow through the cabin heat box from spring through late fall, since so little heat is ever needed in my experience so far.

My mechanic /engine builder suggested I not run more than 6 quarts to avoid blowing excess oil out the breather, but I may try higher levels at some point to see how the consumption is. I plan to change oil this time sooner than 50 hours since I know this batch has been baked to 250 at the sender and inevitably higher temps deep inside the engine. Annual is due netx month anyway.

I think deleting the butterfly is a good idea - fulfills the mandate to "implicate and add lightness." It's only useful in bringing the oil up to operating temp at startup anyway, and that's only an issue when pre-heat is forgotten at home or unavailable away.

Anyone have any thought on reducing the airflow to cylinder 4?

 

[DRMA]

Suggest you check the wire splice between the oil temp probe and the wiring running to your EFIS / Gauge input. I had an issue a couple months ago where the oil temp display showed a very high temp, but when we got it on the ground, it was obvious that the reading was false. I found that the splice between the temp probe and the cable going to the G3X input LRU was intermittent. Replaced the splice and everything is back to normal now.

Not saying this is what is causing your high temp issue, but might be worth checking.

Regards,

 

[Taltruda]

Bill

5 quarts sounds low for a 540. I normally run mine around 9. Max is 12.

regards Peter

Agreed.. 5 quarts on a 540? Yikes!

 

[bjdecker]

I think DanH could add some math here -- I seem to recall that the quantity of oil didn't have an effect on it's temperature, but the rate at which it changed temperature...I could be wrong.

What does the transition from the back baffle to hose, type of hose (SCAT, SCEET, smooth), hose to front of oil cooler interface look like?

Cheers,

B

 

[Skid]

Wife and I started a cross-country to the beach yesterday and we weren’t 15 minutes out when we got an oil temp alarm for 240F. I was in fast cruise-climb and still full rich, with normal CHT’s at the time. I noted the air control knob was sitting slightly back from the full open position. Pushing and holding it in the fully-open position did not alter the trend. I throttled back, trimmed nose down and tried more like 50 fpm but the temp climb continued. When it hit 250F I pulled power and descended to a nearby airport, abandoned on a Sunday morning, and proceeded to pull the upper cowl while things cooled off.

The dipstick read just over 5 quarts, and I normally keep it at 6, so in went the spare quart from the tool kit. No air path obstruction was seen looking down the SCAT and into the cooler mount. I did note the butterfly was cocked a bit from the full open position. Tinkering with the Bowden cable a bit, it looked as if fully open was when the panel knob was about 1/2” out from the panel, so I tried to tape it in that position with electrical tape on the knob shaft. Buttoned things back up and took off, noted Oil T at 170F.

In climb, temp rose slowly as expected and stabilized at about 213-215, which is typical for it. The knob kept creeping out from the panel and I kept shoving it back in to the tape “stop.” Temp would modulate to 220 and back down again each time this happened. We flew the rest of the trip with no issues.

I find it hard to believe that adding a quart of oil made the difference (I always top it at 6qts and add one at 5), and also hard to believe that a slight canting of the butterfly air valve, which was clearly happening, would make the temps exceed redline. In all prior flights and testing, the oil cooler air flow butterfly position has made only about 15 degrees max difference in oil temps - so ineffective that I was considering removing it altogether and possibly just installing a fixed restriction for cold season flying.

Overall, I have been okay with cruise oil temps in the 200-215 range but know they could be better, so I’ve been thinking about adding a bell mouth trumpet to the air intake on the rear baffle over #6. I could also afford to direct some upper cowl airflow away from #4 back to #6 and the oil cooler intake if there is an accepted way to do this. My CHT’s in cruise yesterday were showing #4 about 20F cooler than 2 and 6…

I’m open to suggestions as to cause and cure. I can check the temp sender accuracy in boiling water when I get home in a few days.

Photo is the EFIS in cruise on the second leg after I figured out how to tweak the butterfly for max air flow. #4 is clearly getting more cooling than it needs.

Have you checked the Vernatherm?

 

[bonefishdave]

I think DanH could add some math here -- I seem to recall that the quantity of oil didn't have an effect on it's temperature, but the rate at which it changed temperature...I could be wrong.

Cheers,

B

You are 100 percent correct !

 

[Richard Connell]

Hi Bill.
Interesting timing. Yesterday I removed the butterfly from my oil cooler duct as well. It has been inoperative for 150h due to a failed servo (open thankfully). I’ve expressed the opinion here that these servos are inappropriate in this context due to the consequences of failure. . Enough about that. You have a cable.

What size oil cooler do you have? I assume a 2006X? Are you running a stock IO540?

I changed my oil cooler to a 2007X as many have done with the minor modification to the cooler mount. In cruise up high at high airspeed most of the year I see180 or less.
In summer down low however I’ll see it nudge into the 200s and occasionally 220 (circuits or low slow sightseeing or on the ground after landing) which I don’t like.
I don’t think I’d be happy with 210 all day long personally.
Also I think 5qts sounds low as well. I never run less than 6 on the stick which roughly approximates 8 actually in the engine for me.
Anyway all that said- I removed the butterfly last night and went and shot some night circuits. By the final circuit the OT just touched 200 which is probably 10F cooler than the last time I did some circuits so I do think the butterfly makes a marginal difference- this is rather unscientific tho.

 

[Kyle Boatright]

You are 100 percent correct !

The rate of change would be impacted by the additional 2 pounds of mass per quart. Not much on a 500 lb engine. The other thing which might be in play is the amount of time the oil has in the sump to defroth before being cycled through the system again. Air bubbles don’t transfer heat well. But I doubt that’s the root cause.

For what it is worth, I run 8 quarts in my 540.

 

[jrs14855]

You need to consult the Lycoming specs for the exact engine model. Never heard of level as low as 5 quarts in a 540. We ran 9-10 in the Pitt S2B

 

[Jesse23]

Bill

5 quarts sounds low for a 540. I normally run mine around 9. Max is 12.

regards Peter

66% of 12 = 7.92 (Mike Busch recom) - I keep 8 qts showing and do not not add till it shows below 7 on IO 540. I added 2 tick marks for 7 & 8 qts on the stick.

 

[Webb]

Have you smelled the oil? Does it smell burnt?

 

[Kyle Boatright]

Anyone have any thought on reducing the airflow to cylinder 4?

Easiest thing to do would be modify your inter-cylinder baffles to reduce the size of the opening under #4.

 

[lr172]

Agreed.. 5 quarts on a 540? Yikes!

Care to explain why this is too low? You can't look at this relative to max capacity until you understand why the max is where it is. I suspect many do not understand that.

 

[jrs14855]

Some of the angle valve 360's have a relatively shallow and much wider sump than the paralell valve engines. Those engines have a significantly higher minimum oil level per Lycoming. Soem 540's may be similar.

 

[Taltruda]

Care to explain why this is too low? You can't look at this relative to max capacity until you understand why the max is where it is. I suspect many do not understand that.

Well, you have some 540s that full is 12, and some have full at 8 quarts. FAR 33.39 states that the lubriation system must function properly with half, so that’s 6 quarts. I realize the Lycoming manual has a minimum spec for 2 3/4 quarts in the sump, but is that remaining in the sump while running? I can’t imagine 2 3/4 being enough in the sump before you start.. once the oil pump sucks the sump and moves the oil throughout the engine, there’s not much left in the pan..
Based on my personal experience, I would run a 12 quart 540 at 9 to 10 on the dipstick. If it was down to 8, I would put a quart in. On 4 cylinder engines, I allow it to go to 5, and bring it back up to 6.

 

[RV8JD]

Some of the angle valve 360's have a relatively shallow and much wider sump than the paralell valve engines. Those engines have a significantly higher minimum oil level per Lycoming. Soem 540's may be similar.

As does the parallel valve 180HP IO-360-M1B, -M1A, which have a minimum oil quantity of 4 quarts versus the 2 quart minimum of the other PV (I)O-360 engines.

 

[Avanza]

As does the parallel valve 180HP IO-360-M1B, -M1A, which have a minimum oil quantity of 4 quarts versus the 2 quart minimum of the other PV (I)O-360 engines.

It is important to use the correct oil acording to the surunding air temp.
If you use SAE50 and sorounding air
temp is 40 F the oil will clogg up the
oil cooler and engine oil temp will rise.
If using a multigrade oil this problem
will not ocour.

Good luck

 

[Shays]

I seriously doubt that an extra qt of oil drops temps more than 10 degrees. Most logical guess is that cooling airflow was way down and your butterfly was closed WAY more than you thought it was. I have avoided installing one for reasons like this. I would rather fly around some days with oil at 160 to avoid what happened to you. I will run as low as 4.5 qts on my 10 and have never noticed any higher oil temps than when it has 6 quarts. I am reading capacity level temps (i.e. above VT temps) during the later parts of my climb, so would see the effect there if it existed.

Larry

I am curious, what do you typically run in your -10? I run mine at 9 qts.

 

[Bill Boyd]

On the flight home we never saw OT's above 218F, and they would head back down to 212 every time I pushed the air control knob back in to the position marked by the tape on the shaft as full-open butterfly.

Investigation and remedies ongoing... it's about annual time, anyways...