MikeOH Posted April 5, 2022 Report Posted April 5, 2022 I've fought high oil temps since I bought my F 5 years ago. Always runs at least 200, and more like 220-230 in the summer! As summer is approaching, I'm becoming motivated once again to find the cause. I have had the oil cooler overhauled by Pacific Oil Coolers, replaced the oil hoses to/from the cooler, and at this year's annual I had the vernatherm replaced...nothing has made a difference. I'm beginning to wonder if there is even flow through the cooler, so I'm about to instrument the inlet and outlet fittings with thermocouples. So, my question is how much delta-T should I observe between the oil going in and oil going out? Quote
carusoam Posted April 5, 2022 Report Posted April 5, 2022 Get out the old IR thermometer…. Be on the look out for cold tubes that got blocked… Expect that the cooler OH took care of these… but check anyways…. Got a pic of the front and back of the cooler? That can give hints about the airflow it may have…. Test the vernatherm again… this time watching closely what temperature it opens and closes at… There isn’t much more than that to the whole system… Airflow across the surface area…. Oil flow through the interior… and a valve that controls the oil flow… Check the surface area to see the air can flow on every fin… PP thoughts only, not a mechanic… -a- Quote
tim417 Posted April 5, 2022 Report Posted April 5, 2022 I am a complete newbie and definitely not a mechanic, but I just listened to an AOPA Ask the A&Ps podcast regarding high oil temp readings. The caller had a JPI engine monitor that was reporting 230 but also had the original analog gauge which would consistently report 30 degrees cooler and he wanted to know what the deal is and if there was a problem. Mike Busch and crew determined that the analog oil temp probe was located right after the oil exited the cooler while the JPI monitor probe was somewhere near the front of the block, after the oil has had a chance to absorb much of the heat. The A&Ps said the useful number for the oil temp is at it’s coolest point. Armed with this knowledge, you might want to find out where your oil temp probe is located. 1 Quote
A64Pilot Posted April 5, 2022 Report Posted April 5, 2022 (edited) According to Lycoming there is a 50 f delta on non turbo and 75 on turbo. I chased temps like you have on my Maule until finally determining there was nothing to fix, I called Exxon as I was running Elite at the time wanting to know if I needed to shorten change intervals. They pretty much laughed saying that of course you need to stay within the engine limits, but those are engine limits, it’s not even close to the oils limits, and in fact they from an oils perspective like to see about 200 or slightly higher. Autos often run just tooling around in the 200’s and if pushed just a little, 250 or more. The high performance cars oil coolers are often cooled by engine coolant, which of course runs 195 or higher, so they can’t really cool oil until it’s over 200 or so. Screen shot from an IA renewal class. Now, just an opinion, my opinion is if in cruise it’s 230, then you have something to fix, but if it hits 230 in a climb but runs 200 or so in cruise maybe not. Be sure to climb full rich below 5,000 ft and climb fast, I climb at 110 KIAS for engine cooling, and to cover ground faster. If your climbing at Vy or leaning to target egt, that can be part of the problem. I calling target egt as leaning in the climb to maintain take off egt, there is logic in doing so, unless you have engine cooling problems, then you may want the extra cooling that being excess rich brings. You won’t foul plugs at full throttle in a climb. The below numbers are only valid for temps taken at the factory location of course. On edit, I have the opposite issue on my J, there is nothing I can do short of covering the oil cooler to get temps in the middle of the green, it runs about 1/3. Edited April 5, 2022 by A64Pilot 1 Quote
carusoam Posted April 5, 2022 Report Posted April 5, 2022 Tim, That is a great reminder… 1) Know where the temp is being measured… 2) there is one location that has meaning… the certified location… 3) Over time some instruments may get accidentally relocated… 4) Different locations can have very different temps… 5) Then there is instrument issues… how old are they, are they still in calibration? 6) OilT often use a thermistor sensor… which can drift and go bad over time…. PP thoughts only, not a mechanic… -a- Quote
haymak3r Posted April 5, 2022 Report Posted April 5, 2022 Adding my 2 cents here, (well 1 cent maybe as I am still such a newb).. But when I bought my J, I noticed the oilT was higher than I was used to seeing from the 172 I was flying. The previous owners whom were flying me around to check out the plane said it has been like that as long as they remember. It would creep up to just below the red line... I could tell they were not the most "mechanical" people.. As soon as I purchased it, I asked my mechanic to take a look at the cooler, and vernatherm.. The cooler was flushed but was clear already. The vernatherm was the culprit. It wouldn't open even when the temp was up around 300 degrees!! After replacing that, even in climb my temps don't go above half way. Hopefully your issue is something as easy as this. high oil temps are not good. Good luck! 1 Quote
MikeOH Posted April 5, 2022 Author Report Posted April 5, 2022 Thanks for everyone’s input. Cooler/fins/airflow have been ruled out. Hoses we’re replaced. Vernatherm just replaced with brand new. Temp probe was relocated to factory gauge location. Engine monitor and factory gauge correlate; 220-230 on engine monitor shows a little under redline on factory gauge. Runs those temps in cruise in hot weather. Thanks to @A64Pilot for the delta T info! Is it possible to hook the hoses up incorrectly to the engine? I know there’s a bunch of possible fittings/plugs on the back of the engine. 1 Quote
carusoam Posted April 6, 2022 Report Posted April 6, 2022 Hose routing would be a possible error… unlikely, but possible… Checking them all would be relatively easy… PP thoughts only, not a mechanic… Best regards, -a- 1 Quote
bfreelove Posted April 6, 2022 Report Posted April 6, 2022 I would check the shape of your baffles and seals. Any leakage increases the pressure in the lower plenum and the oil cooler is much more sensitive to this than the cylinders. Ben 1 Quote
MikeOH Posted April 7, 2022 Author Report Posted April 7, 2022 32 minutes ago, bfreelove said: I would check the shape of your baffles and seals. Any leakage increases the pressure in the lower plenum and the oil cooler is much more sensitive to this than the cylinders. Ben @bfreelove Thank you! That is the kind of 'out of the box' thinking I was hoping for. I NEVER would have thought of that possibility. 1 Quote
M20F Posted April 7, 2022 Report Posted April 7, 2022 If you have the relocated cooler on your F then make sure the gaps in the doghouse are filled up with RTV around the cooler. That is a cheap easy one. Would agree with balance after that check the gauge is right. Quote
MikeOH Posted April 7, 2022 Author Report Posted April 7, 2022 @M20F Thanks. Stock cooler location. I suppose it could be the gauge, but I have two: the factory gauge and the G3 Insight. When the G3 is showing near 230, the factory gauge is close to red line. I also had the G3 probe relocated from the front of the engine (read 10 degrees hotter there!) to the same location as the factory gauge. It's really like the cooler just isn't cooling; that's why I want to look at inlet and outlet temps....my gut is telling me there is going to be way less than a 50 degree delta. A loss in delta P across the cooler, as @bfreelove mentioned, would be a very plausible explanation for cooler ineffectiveness. Quote
M20F Posted April 7, 2022 Report Posted April 7, 2022 13 minutes ago, MikeOH said: @M20F Thanks. Stock cooler location. I suppose it could be the gauge, but I have two: the factory gauge and the G3 Insight. When the G3 is showing near 230, the factory gauge is close to red line. I also had the G3 probe relocated from the front of the engine (read 10 degrees hotter there!) to the same location as the factory gauge. It's really like the cooler just isn't cooling; that's why I want to look at inlet and outlet temps....my gut is telling me there is going to be way less than a 50 degree delta. A loss in delta P across the cooler, as @bfreelove mentioned, would be a very plausible explanation for cooler ineffectiveness. 2 gauges but are they using the same probe? Baffling could be an issue but given it is on the front directly in the airflow I doubt it. Quote
MikeOH Posted April 7, 2022 Author Report Posted April 7, 2022 6 minutes ago, M20F said: 2 gauges but are they using the same probe? Baffling could be an issue but given it is on the front directly in the airflow I doubt it. @M20F No, separate probes; one factory, one for the G3. Perhaps, but the idea that if the pressure in the lower plenum is higher than it should be, it would reduce airflow through the cooler is logical. I'm running out of ideas, so I'm open to just about anything! I am going to check where the hoses attach to the accessory case; a little research has revealed that it's different for the O-360 vs the IO-360. Not sure the accessory case would allow it on my IO-360 but it's easy to check. Quote
carusoam Posted April 7, 2022 Report Posted April 7, 2022 MikeOH, Did you see the note from Paul Lowen either above or in a post from yesterday… He is the original Paul of Lasar…. He is using his wife’s ID… sheryL Somewhere along the history of Mooney… somebody stated that the airflow through the oil cooler is actually running in reverse…. Paul just mentioned it again yesterday… That makes it a bit more challenging to see the airflow…. The seals still make sense to purse… But the source of air pressure behind the oil cooler needs to be checked for its health too… More like being on the look out for all seals that may be compromised… My M20C left all kinds of indications of the air flowing out the front of the cowl… with oil and grease… Best regards, -a- Quote
MikeOH Posted April 7, 2022 Author Report Posted April 7, 2022 @carusoam Thanks! I had not seen Paul's post. It wasn't clear whether the forward airflow was for all Mooney models, or just those with a dog house. I admit, it is pretty hard to fathom air flowing forward when the cooler is only inches from the back of prop!! If so, however, then perhaps my issue is NOT enough pressure in the lower plenum. As you say, either scenario may be due to poor seals. And, I've always fought high CHT on #2, as well. 1 Quote
Ragsf15e Posted April 7, 2022 Report Posted April 7, 2022 18 hours ago, MikeOH said: @carusoam Thanks! I had not seen Paul's post. It wasn't clear whether the forward airflow was for all Mooney models, or just those with a dog house. I admit, it is pretty hard to fathom air flowing forward when the cooler is only inches from the back of prop!! If so, however, then perhaps my issue is NOT enough pressure in the lower plenum. As you say, either scenario may be due to poor seals. And, I've always fought high CHT on #2, as well. Have you played with cowl flaps in cruise and see if it helps? It only takes a small change to affect the pressure in the bottom and thus the airflow over the cooler. Maybe they aren’t set right? Also, maybe I missed it, but what are your typical cruise chts and oat? I see 180-190 oil temp in my F but I’m typically running chts ~320 (or colder) and cold oat since I’m at higher altitude (lower power) and in Washington. Quote
N201MKTurbo Posted April 7, 2022 Report Posted April 7, 2022 (edited) You could recut the vernatherm seat. I did it on my old F Mooney and it helped. It can be done by just removing the vernatherm. Put grease on the cutter to catch the chips. The only problem is finding the tool. I knew the owner of the engine shop and he loaned me his tool. Its not something most mechanics would have. https://vansairforce.net/community/showthread.php?t=188143 Edited April 7, 2022 by N201MKTurbo 1 Quote
MikeOH Posted April 8, 2022 Author Report Posted April 8, 2022 4 hours ago, Ragsf15e said: Have you played with cowl flaps in cruise and see if it helps? It only takes a small change to affect the pressure in the bottom and thus the airflow over the cooler. Maybe they aren’t set right? Also, maybe I missed it, but what are your typical cruise chts and oat? I see 180-190 oil temp in my F but I’m typically running chts ~320 (or colder) and cold oat since I’m at higher altitude (lower power) and in Washington. @Ragsf15e Haven't really noticed a change with cowl flaps, but worth a deliberate test to quantify. Here's my CHTs, oil temp in cruise, and OAT (note close to 80 on the ground, only 63 in cruise): Quote
MikeOH Posted April 8, 2022 Author Report Posted April 8, 2022 4 hours ago, N201MKTurbo said: You could recut the vernatherm seat. I did it on my old F Mooney and it helped. It can be done by just removing the vernatherm. Put grease on the cutter to catch the chips. The only problem is finding the tool. I knew the owner of the engine shop and he loaned me his tool. Its not something most mechanics would have. https://vansairforce.net/community/showthread.php?t=188143 @N201MKTurbo Interesting you bring up the seat....at annual, when I had the vernatherm replaced, my mechanic said the seat was a little rough and he 'cleaned it up'. Not sure how, and given the cost of the tool, I'm wondering if that's where the problem is! That is, maybe he didn't really correct the problem. If I want to replace the seat I need an entire new oil filter adaptor as the vernatherm threads into it, I believe. Quote
Ragsf15e Posted April 8, 2022 Report Posted April 8, 2022 27 minutes ago, MikeOH said: @Ragsf15e Haven't really noticed a change with cowl flaps, but worth a deliberate test to quantify. Here's my CHTs, oil temp in cruise, and OAT (note close to 80 on the ground, only 63 in cruise): Chts seem ok. How high were you? 60s oat is good at low altitude but potentially warm if up high. I definitely notice a difference with the thin air at altitude not cooling as well, especially when warm. However I’m talking 10,000’ plus. Your chts and oat seem normal but you’re right, oil temp seems high. Quote
MikeOH Posted April 8, 2022 Author Report Posted April 8, 2022 @carusoam I think you've got it 180 off. When cold the valve is off the seat and oil bypasses the cooler. When warm the vernatherm expands and seals against the seat and the oil is forced to route through the cooler. If the seat leaks, then not all oil will go to the cooler. As mentioned in my previous posts, the cooler was overhauled by Pacific Oil Coolers...there was no improvement after OH, nor has it become worse. So, I really don't see how any tubes are blocked. 1 Quote
MikeOH Posted April 8, 2022 Author Report Posted April 8, 2022 1 hour ago, Ragsf15e said: Chts seem ok. How high were you? 60s oat is good at low altitude but potentially warm if up high. I definitely notice a difference with the thin air at altitude not cooling as well, especially when warm. However I’m talking 10,000’ plus. Your chts and oat seem normal but you’re right, oil temp seems high. @Ragsf15e I was at 6500 Quote
carusoam Posted April 8, 2022 Report Posted April 8, 2022 Sounds like all of the bases are covered… How does one check the airflow..? Got a Go pro? A GoPro and a telltale….. Would make an interesting Mooney centric video…. Thanks for correcting my logic above… I’ll be removing it to not cause any additional confusion for somebody… Best regards, -a- Quote
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