Scary High Oil Temps - Lycoming 540

bnt83 said:
Looks a lot like an oil leak
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It IS an oil leak, and it's why the cooler is wet there. It's seeping oil. Those ridges are welded together to form the cooler channels, and that chafed area has worn though the weld. That oil cooler was junk a long time ago.

Cessna wants oil cooler on their airplanes to be flushed every 1000 hours. Crud builds up inside them. And even with flushing, varnish gradually forms on the inside surfaces, insulating the hot oil from the cooling metal. We once had a 172 that ran hot right after we installed a new engine. Hotter is normal, but redline is not, and I had to keep terminating the test flights due to redline oil temps. The gauge checked out accurate. The oil cooler airflow was right. The engine oil system plumbing, internally and externally, was all right. The cooler had been flushed at engine change, and flushing it again made no difference.

A new oil cooler fixed the problem instantly. Varnish in the old one. Look inside an engine's crankcase sometime; if it's got lots of hours on it, it's all nice and brown inside. Varnish.
 
Dan Thomas said:
It IS an oil leak, and it's why the cooler is wet there. It's seeping oil. Those ridges are welded together to form the cooler channels, and that chafed area has worn though the weld. That oil cooler was junk a long time ago.

Cessna wants oil cooler on their airplanes to be flushed every 1000 hours. Crud builds up inside them. And even with flushing, varnish gradually forms on the inside surfaces, insulating the hot oil from the cooling metal. We once had a 172 that ran hot right after we installed a new engine. Hotter is normal, but redline is not, and I had to keep terminating the test flights due to redline oil temps. The gauge checked out accurate. The oil cooler airflow was right. The engine oil system plumbing, internally and externally, was all right. The cooler had been flushed at engine change, and flushing it again made no difference.

A new oil cooler fixed the problem instantly. Varnish in the old one. Look inside an engine's crankcase sometime; if it's got lots of hours on it, it's all nice and brown inside. Varnish.
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So... two mechanics concur, that's an oil leak :yeahthat:
 
SixPapaCharlie said:
I know. Next time I have money burning a hole in my pocket I am getting some sort of engine monitor.
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I'm guessing that will be about the same time you spend about $50-80k on a new engine.
 
EdFred said:
Nuke it from orbit. It's the only way to be sure.
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I don't know maybe he can fill it with something fun like a yellow mystery liquid, attach it to a compressor and see what happens for one of his videos.
 
Dan Thomas said:
Cessna wants oil cooler on their airplanes to be flushed every 1000 hours. Crud builds up inside them. And even with flushing, varnish gradually forms on the inside surfaces, insulating the hot oil from the cooling metal. We once had a 172 that ran hot right after we installed a new engine. Hotter is normal, but redline is not, and I had to keep terminating the test flights due to redline oil temps. The gauge checked out accurate. The oil cooler airflow was right. The engine oil system plumbing, internally and externally, was all right. The cooler had been flushed at engine change, and flushing it again made no difference.

A new oil cooler fixed the problem instantly. Varnish in the old one. Look inside an engine's crankcase sometime; if it's got lots of hours on it, it's all nice and brown inside. Varnish.
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Does a trip to Pacific Oil Cooler for overhaul/flush clean out the varnish?

My RV-8 has a somewhat similar oil temp issue; after a top overhaul a coupla years ago on my O-360, my oil temps were elevated a bit, not to redline or anything, but at least 15 deg warmer than usual. While the cylinders were off I also did a mineral spirits soak and flush of the cooler. After flying with these elevated temps for awhile I replaced the vernatherm with new since the engine (and cooler) are approaching 2200 hrs. No change. So, now I’m wondering if I need to send cooler for a proper overhaul… or replace?
 
jbDC9 said:
Does a trip to Pacific Oil Cooler for overhaul/flush clean out the varnish?

My RV-8 has a somewhat similar oil temp issue; after a top overhaul a coupla years ago on my O-360, my oil temps were elevated a bit, not to redline or anything, but at least 15 deg warmer than usual. While the cylinders were off I also did a mineral spirits soak and flush of the cooler. After flying with these elevated temps for awhile I replaced the vernatherm with new since the engine (and cooler) are approaching 2200 hrs. No change. So, now I’m wondering if I need to send cooler for a proper overhaul… or replace?
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In my experience, flushing with solvent doesn't do a lot of good. You'll get some stuff out but it won't all come out and a lot of varnish will be left behind. The Pacific Oil Cooler treatment will get things out of a cooler that you couldn't otherwise touch. I'm not convinced their cleaning makes them as good as new but it will be far better than what you could do in a typical workshop.

As an aside, the oil flows through the oil cooler first then heads to the oil filter. In other words, the cooler ends up as sort of a pre-filter. If a cooler has been run for a long time without a good cleaning it will probably have a bunch of metal in it that should be flushed out.
 
If the new cooler and baffling still doesn't solve your problem it's pretty easy to verify the gauge accuracy.
 
I thought you boil water when your wife is having a baby
 
SixPapaCharlie said:
Boiling water?
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That is an easy check but will only give you the option to check temperatures at or below 100 degrees C. The thermistors that are commonly used in these instrument clusters are often nonlinear, so I would want to check a wider range if possible. Especially since the belief is that your oil temperature is high. I’d use oil or some other liquid that could be heated to a hotter temperature without boiling and a thermocouple as a reference. Making sure the sensor circuit is solid and complete is important too.
 
mondtster said:
That is an easy check but will only give you the option to check temperatures at or below 100 degrees C. The thermistors that are commonly used in these instrument clusters are often nonlinear, so I would want to check a wider range if possible. Especially since the belief is that your oil temperature is high. I’d use oil or some other liquid that could be heated to a hotter temperature without boiling and a thermocouple as a reference. Making sure the sensor circuit is solid and complete is important too.
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The boiling water is at 212F. Oil temp redline is typically 245F. Boiling water is close rnough, and I used it many times. If you use oil and a thermometer, you're at the mercy of the thermometer's accuracy, and without formal calibration, you don't know where you're at.

I used a candy thermometer in the water. It was accurate enough at room temp and boiling, so everything in between was ok.
 
Dan Thomas said:
The boiling water is at 212F. Oil temp redline is typically 245F. Boiling water is close rnough, and I used it many times. If you use oil and a thermometer, you're at the mercy of the thermometer's accuracy, and without formal calibration, you don't know where you're at.

I used a candy thermometer in the water. It was accurate enough at room temp and boiling, so everything in between was ok.
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That’s why I would use a thermocouple. And I do calibration and instrumentation for a living.

Edit: Perhaps I should be more clear. Generally speaking, thermocouples and their measurement devices can go without a calibration and provide adequate results. In the test lab we only calibrate thermocouples for very select tests and even then, the calibrated temperature source we are using to warm the thermocouple up to the desired temperature to perform the calibration is off less than 1/2 a degree in most cases. I'd have no qualms about plugging a thermocouple into my Fluke meter and winging it in this case.

Personally, I'd want to check the aircraft's instrument up to about 125 or 130 degrees C.
 
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tsts4 said:
Interesting redline on that gauge. The Lycoming Operators Manual states the max oil temp for 540s is 245* F and recommends for max engine life keeping it between 165* and 200* in level flight, cruise conditions.
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During summer months we consistently saw about 215F Oil temp in full power glider tow operations. The O-540 was configured with two oil coolers for this operation.
 
Mineral spirits are a weak solvent, and likely to be no benefit in cleaning out varnish in the oil cooler.

While I haven't used them in that particular application, I think acetone, hexane, and toluene would be effective. I'm sure some will recoil in horror at the idea of the average bumbling do-it-yerselfer handling these chemicals, but normal precautions and personal protective gear is adequate to mitigate those concerns.
 
There was a mention that the oil is routed through the oil cooler before the filter. Why not in reverse of that order?

Tim
 
tspear said:
There was a mention that the oil is routed through the oil cooler before the filter. Why not in reverse of that order?

Tim
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I don’t know why they do it that way, but it is a common thing, even in modern engines made by various manufacturers in all sorts of different applications. In fact, most or maybe even all of them I’ve seen are like that.
 
3393RP said:
Mineral spirits are a weak solvent, and likely to be no benefit in cleaning out varnish in the oil cooler.

While I haven't used them in that particular application, I think acetone, hexane, and toluene would be effective. I'm sure some will recoil in horror at the idea of the average bumbling do-it-yerselfer handling these chemicals, but normal precautions and personal protective gear is adequate to mitigate those concerns.
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I would be concerned that the "wrong" stuff would peel the varnish off rather than dissolve it, and then the debris would start plugging cooler channels or hoses.
 
SixPapaCharlie said:
I know. Next time I have money burning a hole in my pocket I am getting some sort of engine monitor.
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cowman said:
Do you have an engine analyzer or another source for oil temp... or CHTs or something? I'd want to verify the gauge's accuracy. I cannot recommend an engine analyzer enough- they get your attention faster than the old needle gauges and being able to look at all the individual CHT/EGTs can save a lot of time troubleshooting.
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SixPapaCharlie said:
I told him not to spend any time on it just put a new one in. Anything that looks like that, it's not going to hurt to replace. $500 now or $500 later.
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Use the $500 here and $500 there and get the engine monitor now, and make sure you get one that logs data. Of all the aircraft upgrades you can do, this one is by far the most likely to pay for itself IMO.

Example: You get out to the runway and you notice roughness on your mag check. No engine monitor: "Hey Tom, I had some roughness on my mag check, can you tear my engine apart looking for the culprit?" With engine monitor: "Hey Tom, can you please replace the bottom spark plug on the #3 cylinder for me?" That'll be worth at least a couple hundred bucks in diagnostic time.

Another example: We had a pilot in the flying club report high CHT on one particular cylinder. I looked at the logged data files and found that cylinder had always been the hottest. I also found online where the owner of a plane two serial numbers away from ours had posted his data for public consumption online, and discovered that his same-numbered cylinder also ran hotter than the rest. In addition, for both, I was able to determine that the temp shown was never out of line for the power settings and environmental conditions. Total shop cost: $0.

In your example: You'd be able to tell whether this is something that happened suddenly, or something that was slow-onset, or something that really wasn't out of line at all but you didn't even know it because you have other things to look at while the plane is flying. Something sudden, yeah, something is probably broken. Slow onset, something may be worn out. Or you may find it's all in your head and it's always been that way and it's perfectly normal, or at least reasonably close to normal.

Logging engine monitors are a no-brainer upgrade. If you can also install something that logs things like airspeed and OAT, even better. And if you aren't an expert at data analysis, there are sites like Flysto and services like Savvy Analysis that can help you out.
 
flyingcheesehead said:
Use the $500 here and $500 there and get the engine monitor now, and make sure you get one that logs data. Of all the aircraft upgrades you can do, this one is by far the most likely to pay for itself IMO.

Example: You get out to the runway and you notice roughness on your mag check. No engine monitor: "Hey Tom, I had some roughness on my mag check, can you tear my engine apart looking for the culprit?" With engine monitor: "Hey Tom, can you please replace the bottom spark plug on the #3 cylinder for me?" That'll be worth at least a couple hundred bucks in diagnostic time.

Another example: We had a pilot in the flying club report high CHT on one particular cylinder. I looked at the logged data files and found that cylinder had always been the hottest. I also found online where the owner of a plane two serial numbers away from ours had posted his data for public consumption online, and discovered that his same-numbered cylinder also ran hotter than the rest. In addition, for both, I was able to determine that the temp shown was never out of line for the power settings and environmental conditions. Total shop cost: $0.

In your example: You'd be able to tell whether this is something that happened suddenly, or something that was slow-onset, or something that really wasn't out of line at all but you didn't even know it because you have other things to look at while the plane is flying. Something sudden, yeah, something is probably broken. Slow onset, something may be worn out. Or you may find it's all in your head and it's always been that way and it's perfectly normal, or at least reasonably close to normal.

Logging engine monitors are a no-brainer upgrade. If you can also install something that logs things like airspeed and OAT, even better. And if you aren't an expert at data analysis, there are sites like Flysto and services like Savvy Analysis that can help you out.
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My aviation budget is funded one funny video at a time lol!
Engine monitors are a little out of my budget currently. Like and Subscribe.
 
SixPapaCharlie said:
Not yet. I am in ATP - CPT training through next week.
I am having all my baffling replaced as well while I am out for training.
It was in terrible shape and not helping matters.
I likely wont be able to fly until next weekend.
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:fcross:
 
Grum.Man said:
It doesn't need to be boiling, just needs to be a known temp. Heat some water up in a cup, put a digital temp probe in it and dunk the temp sensor in and compare the readings.
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Which is hotter, 200* water or 200* oil?
 
flyingcheesehead said:
Logging engine monitors are a no-brainer upgrade. If you can also install something that logs things like airspeed and OAT, even better.
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Cars have had this stuff for a long time, and their engines don't cost nearly as much as an aircraft engine. If the monitor can save on diagnostic times and engine damage. it might be worth it.

But once most airplanes have it, we'll have a new generation of A&Ps that need the computer to tell them what to fix. The owners of airplanes without a monitor will have to talk some old, long-retired mechanic into coming to look at his airplane.
Grum.Man said:
It doesn't need to be boiling, just needs to be a known temp.
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The whole idea of boiling water is that it boils at 212°F at sea level, and no amount of further heating will raise it above boiling. It just boils harder and evaporates faster. It's a fixed, reliable value, needing no thermometer. as long as the water contains no salts or other contaminants. And if the testing is being done at a higher airport, the boiling point is easily determined by a quick internet search.

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Dan Thomas said:
Cars have had this stuff for a long time, and their engines don't cost nearly as much as an aircraft engine. If the monitor can save on diagnostic times and engine damage. it might be worth it.

But once most airplanes have it, we'll have a new generation of A&Ps that need the computer to tell them what to fix. The owners of airplanes without a monitor will have to talk some old, long-retired mechanic into coming to look at his airplane.
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Disagree. It's not like these systems are integrated into the airframe, or even the engine, with sensors for various parts and the ability to determine what might be wrong or need replacing. It's simple temperatures. The monitor doesn't even know what engine it's on, much less what airframe, so A&Ps will still need the same skills.

However, those that develop skills around looking at engine and even flight data will be able to charge a premium per hour, because they'll be able to finish things quicker without having to take so many things apart to diagnose. It's a different skill, though, much like electrical systems or avionics are often out of the wheelhouse of the more mechanically-minded A&Ps.
 
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