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High Oil temp - Also

E

ebackscheider

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I didn't want to hijack the other threat Latech15 has, but I'm in a similar battle. I've read many posts on the topic, as well as Lycoming's docs.

I'm looking for anything glaring I missed before I start changing big things, like the cooler itself. New fuel and Oil hoses in the last 6 months, but this problem was before and after. I have Surefly on the left and a new slick on the right at 25 degrees, and I verified them both again.

RV6, O360, 850 hours on 25yr old motor. I do tend to run at 2550 and the stats from my last XC are...
OAT - 68 deg
CHT 350, 385, 392, 368
FF 11.8 - would love to see this come down, but if I lean any further, #3 CHT breaks 400 at this power setting.
RPM 2585
Manifold 20.1
Alt 8,500
Dynon says 61% power
Oil Temp 221


My real questions are. Do I build exit duct work to widen it up? Do I replace/inspect the vernatherm? Do I just replace the oil cooler with one that has more rows, which might mean fabrication and moving it to remote?

I didn't build this plane, this was all pretty much the way it came, outside of me removing a block on the back of the cooler and RTV'ing the baffle to seal it up better.


20241124_185228869_iOS.jpg20241124_185314120_iOS.jpg20241124_185521128_iOS.jpg​

 
At that power setting, OAT and fuel flow, I would expect cooler oil temps and CHTs. Not that the CHTs are high, but they seem higher than I would think with the conditions you've stated. The three most common causes of a hot running engine are timing, fuel flow, or baffles. Since the timing is confirmed good and your fuel flow seems in the ballpark, I'd be looking at the baffles and baffle seals first. If you're not sure what "good" baffles are, do a search on this forum, as cooling is a source of frustration for many RV-ers. Dan Horton has some of the best pics and explanations on this subject on the VAF. There are also some good videos out there that are worth a look. Get the baffles as good as they can be first, then see if you still need to do something with the cooler.

Also, what is the schmutz on the fins of the oil cooler?
 
If I'm doing the math properly, you're about 22 deg C above standard OAT there at 8500', so that's got to be part of the problem. The junk in your oil cooler probably isn't helping. If you can flush that out, I'd bet it would reduce your oil temperatures at least a little.

I've got the smaller cooler on my RV6 as well, but it's mounted up front by the inlet. Even so, in the summer when it's 110 degrees outside, the oil does get warm.

--Ron
 
I'd start by swapping out the oil cooler for a more efficient model - Southind/SW/Meggitt 8406R or Aeroclassic HE 8001602.
 
Install a viscosity valve and see what happens. Very easy and inexpensive way to rule out a bad seat or malfunctioning wax pellet.
 
ronrapp said:
If I'm doing the math properly, you're about 22 deg C above standard OAT there at 8500', so that's got to be part of the problem. The junk in your oil cooler probably isn't helping. If you can flush that out, I'd bet it would reduce your oil temperatures at least a little.

I've got the smaller cooler on my RV6 as well, but it's mounted up front by the inlet. Even so, in the summer when it's 110 degrees outside, the oil does get warm.

--Ron
Click to expand...

D-Dubya said:
At that power setting, OAT and fuel flow, I would expect cooler oil temps and CHTs. Not that the CHTs are high, but they seem higher than I would think with the conditions you've stated. The three most common causes of a hot running engine are timing, fuel flow, or baffles. Since the timing is confirmed good and your fuel flow seems in the ballpark, I'd be looking at the baffles and baffle seals first. If you're not sure what "good" baffles are, do a search on this forum, as cooling is a source of frustration for many RV-ers. Dan Horton has some of the best pics and explanations on this subject on the VAF. There are also some good videos out there that are worth a look. Get the baffles as good as they can be first, then see if you still need to do something with the cooler.

Also, what is the schmutz on the fins of the oil cooler?
Click to expand...
I agree, the baffling should be re-done. I’ll look up Dan’s stuff. I can only guess that someone covered it up at one point, and tried to undo it. I’ve pulled a lot out already, which is why I was leaning toward a replacement anyhow.
 
The small portion of the baffles that are visible look pretty bad. Seal material definitely needs replacing and the center seal portion may be missing. Also apparently not secured adequately to the metal portion.
Having said that the oil temp is not that bad considering the high ambient temperature.
Fuel consumption is not that bad considering the r/m.
Complete baffle replacement might be necessary.
 
A few thoughts:
- #3 CHT is the highest. Try the “adding the washer trick” between the rear baffle the #3 cylinder (as in screw, baffle wall, washer, cylinder). The promotes a little more air to #3.
- Your fuel flow is way high. I understand you do this to keep CHTs reasonable but this is not a condition I would tolerate. At that altitude and power setting I’m at ~7.8gph.
- Along that line, are you really sure the Surefire is at 25 degrees? I’m not familiar with the Surefire but I have found Lightspeed ignitions where the new owner could not keep CHTs below 400 degrees. One was the classic “set the timing at 25 degrees BTDC, not TDC per the instructions”. The other was a failed MAP circuit that put 40 degrees of timing advance on the engine regardless of RPM or MP. Here, verify the Surefire timing with a timing light to find truth. In your case I’d do this before next flight.
- Look for airleaks on the cylinder intake tubes. Replacing the cylinder head to intake tube gaskets is cheap insurance.
- That Positec cooler was the standard offered by Van’s around that time. Not the best and in fact there was a recall to upgrade to a “new improved” Positec at no cost (then Van’s dropped this vendor). As this cooler is 20+ years old and I’d guess never cleaned, I suggest replacing it with the same size Airflow Systems cooler. I’m guessing you have the 10 row size, so the Airflow 2004X.
- I have never been a fan of baffle mounted oil coolers, but if a simple swap does the trick I’d go with what you have.
- Keep in mind going ~20 degrees LOP will drop your CHTs 10-20 degrees. But don’t try this before solving your potential timing problem.

Carl
 
jrs14855 said:
The small portion of the baffles that are visible look pretty bad. Seal material definitely needs replacing and the center seal portion may be missing. Also apparently not secured adequately to the metal portion.
Having said that the oil temp is not that bad considering the high ambient temperature.
Fuel consumption is not that bad considering the r/m.
Complete baffle replacement might be necessary.
Click to expand...

Here is a better view, but yes, I think this needs to be re-done. Also, I've never had baffling around the nose at all.
20241125_140245334_iOS.jpg20241125_131448806_iOS.jpg
 
Carl Froehlich said:
A few thoughts:
- #3 CHT is the highest. Try the “adding the washer trick” between the rear baffle the #3 cylinder (as in screw, baffle wall, washer, cylinder). The promotes a little more air to #3.
- Your fuel flow is way high. I understand you do this to keep CHTs reasonable but this is not a condition I would tolerate. At that altitude and power setting I’m at ~7.8gph.
- Along that line, are you really sure the Surefire is at 25 degrees? I’m not familiar with the Surefire but I have found Lightspeed ignitions where the new owner could not keep CHTs below 400 degrees. One was the classic “set the timing at 25 degrees BTDC, not TDC per the instructions”. The other was a failed MAP circuit that put 40 degrees of timing advance on the engine regardless of RPM or MP. Here, verify the Surefire timing with a timing light to find truth. In your case I’d do this before next flight.
- Look for airleaks on the cylinder intake tubes. Replacing the cylinder head to intake tube gaskets is cheap insurance.
- That Positec cooler was the standard offered by Van’s around that time. Not the best and in fact there was a recall to upgrade to a “new improved” Positec at no cost (then Van’s dropped this vendor). As this cooler is 20+ years old and I’d guess never cleaned, I suggest replacing it with the same size Airflow Systems cooler. I’m guessing you have the 10 row size, so the Airflow 2004X.
- I have never been a fan of baffle mounted oil coolers, but if a simple swap does the trick I’d go with what you have.
- Keep in mind going ~20 degrees LOP will drop your CHTs 10-20 degrees. But don’t try this before solving your potential timing problem.

Carl
Click to expand...

No, never cleaned that I know of.

7.8, is that a Fixed Pitch, Carb version? I can only dream of that FF.
 
ebackscheider said:
Here is a better view, but yes, I think this needs to be re-done. Also, I've never had baffling around the nose at all.
View attachment 75090View attachment 75091
Click to expand...
I think we have a winner!! That set-up is dumping a lot of air from top to bottom that never has a chance to do any cooling. Yes, all of those other things people have listed may need to be checked as well--and none of them will take a lot of time. But you gotta get that baffling and seals in order to give it a fighting chance.

Take a look at this thread; it has some good information with really good photos: https://vansairforce.net/threads/baffling-clean-up.229364/page-2
 
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D-Dubya said:
I think we have a winner!! That set-up is dumping a lot of air from top to bottom that never has a chance to do any cooling. Yes, all of those other things people have listed may need to be checked as well--and none of them will take a lot of time. But you gotta get that baffling and seals in order to give it a fighting chance.

Take a look at this thread; it has some good information with really good photos: https://vansairforce.net/threads/baffling-clean-up.229364/page-2
Click to expand...
Thank you! I need to order the aluminum to make the nose, can you tell me why is standard to use?
 
ebackscheider said:
Thank you! I need to order the aluminum to make the nose, can you tell me why is standard to use?
Click to expand...
I think all of those parts were made of 0.032" sheet. Van's Store may sell the individual components that are already cut to size and pre-bent. You'll just need to find the drawing for your engine and order those numbered components. It'll save you a lot of time, as those parts have a lot of twists and bends.
 
D-Dubya said:
I think all of those parts were made of 0.032" sheet. Van's Store may sell the individual components that are already cut to size and pre-bent. You'll just need to find the drawing for your engine and order those numbered components. It'll save you a lot of time, as those parts have a lot of twists and bends.
Click to expand...
Thank you!
 
ebackscheider said:
I didn't want to hijack the other threat Latech15 has, but I'm in a similar battle. I've read many posts on the topic, as well as Lycoming's docs.

I'm looking for anything glaring I missed before I start changing big things, like the cooler itself. New fuel and Oil hoses in the last 6 months, but this problem was before and after. I have Surefly on the left and a new slick on the right at 25 degrees, and I verified them both again.

RV6, O360, 850 hours on 25yr old motor. I do tend to run at 2550 and the stats from my last XC are...
OAT - 68 deg
CHT 350, 385, 392, 368
FF 11.8 - would love to see this come down, but if I lean any further, #3 CHT breaks 400 at this power setting.
RPM 2585
Manifold 20.1
Alt 8,500
Dynon says 61% power
Oil Temp 221


My real questions are. Do I build exit duct work to widen it up? Do I replace/inspect the vernatherm? Do I just replace the oil cooler with one that has more rows, which might mean fabrication and moving it to remote?

I didn't build this plane, this was all pretty much the way it came, outside of me removing a block on the back of the cooler and RTV'ing the baffle to seal it up better.


View attachment 75035View attachment 75036View attachment 75037​

Click to expand...
* row oil coolers are inadaquate, 9 row if it is a SW dual pass, otherwise if the engine is "pumped up" at all or has piston squirters, a 10 row. But first, I would try retarding the timing just a bit. A standard 180- HP engine can run at 25 BTDC, but if pumped up at al;, needs to run at 20 BTDC. ( For the Pmag guys, thats 5 degrees AFTER TDC. Each tooth is 2.8 degrees, so 2 teeth. Makes a big difference in CHT.
DAR Gary
 
I have to disagree with post 13. 0 320 with 10-1 pistons, no other engine mods. NO piston squirters. 7 row cooler set back from #3 cylinder and tilted back and away from the cylinder. Very small cowl inlet and outlet with plenum and cowl flap. Cruise CHT is slightly below 350 which is just where I want it. Oil temp ranges from a bit too cool at altitude to a bit too hot last summer when the ambient temps were extremely high. I do not have an exit duct on the cooler but have been thinking about installing one. Also considering a flow control for oil line to cooler.
Bendix mag set at 22 degrees for engine break in, now at 25 degrees. Wittman Tailwind with Whirlwind GA prop
I put 1000 hours on a Pitts S1S, stock 0 360 turning as high as 3500 r/m. Oil temp would get to 200 on a hot day, 100 degree plus ambient.
 
jrs14855 said:
I have to disagree with post 13. 0 320 with 10-1 pistons, no other engine mods. NO piston squirters. 7 row cooler set back from #3 cylinder and tilted back and away from the cylinder. Very small cowl inlet and outlet with plenum and cowl flap. Cruise CHT is slightly below 350 which is just where I want it. Oil temp ranges from a bit too cool at altitude to a bit too hot last summer when the ambient temps were extremely high. I do not have an exit duct on the cooler but have been thinking about installing one. Also considering a flow control for oil line to cooler.
Bendix mag set at 22 degrees for engine break in, now at 25 degrees. Wittman Tailwind with Whirlwind GA prop
I put 1000 hours on a Pitts S1S, stock 0 360 turning as high as 3500 r/m. Oil temp would get to 200 on a hot day, 100 degree plus ambient.
Click to expand...
No worries. My motor is not hopped up. Very stock O360 with FP prop.

I think baffles are the glaring issue. Never knew those front ones existed. I might do the cooler if the problems persist.

Thanks,
Eric
 
Some relevant baffle drawings for the front pieces. Confirms as stated above by D-Dubya, 0.032 either 2024T3 or 6061T6. Some parts are 0.040.

IMG_0354.jpegIMG_0354.jpegIMG_0355.jpeg
 
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Eric,
As said, not having any baffling in the nose area of the engine is a huge air leak. I’ve read that a 1 square inch leak in the baffle sealing can account for up to a 20% loss in cooling efficiency. Everything in that high pressure upper plenum area suffers from any loss - cylinders, oil cooler, everything. My baffle kit from Vans was missing two critical baffle pieces and were placed on back order. I had (have) full size RV6 plans and just made my own missing pieces. I think I still have those full size drawings (RV6, O-360), and you can use them as a template to make what you need. I just cut out the pieces from the full size drawings to make the two parts that I needed. I think the drawing for the pieces you need are still intact. Let me know if you want them and I’ll look for them. Incidentally, my 7 row oil cooler is mounted on the firewall fed by a 3” scat hose from the #4 baffle. I have trouble getting my oil to warm up enough. I had to put in a cockpit controlled butterfly valve in the opening, and even fully closed in the winter, I’m lucky to get up to 160*.
Also - my FF at 65% power (O-360, carb, fixed pitch) is 7.8 to 8 gph. Let me know if you need these drawings.
 
Scott Hersha said:
Eric,
As said, not having any baffling in the nose area of the engine is a huge air leak. I’ve read that a 1 square inch leak in the baffle sealing can account for up to a 20% loss in cooling efficiency. Everything in that high pressure upper plenum area suffers from any loss - cylinders, oil cooler, everything. My baffle kit from Vans was missing two critical baffle pieces and were placed on back order. I had (have) full size RV6 plans and just made my own missing pieces. I think I still have those full size drawings (RV6, O-360), and you can use them as a template to make what you need. I just cut out the pieces from the full size drawings to make the two parts that I needed. I think the drawing for the pieces you need are still intact. Let me know if you want them and I’ll look for them. Incidentally, my 7 row oil cooler is mounted on the firewall fed by a 3” scat hose from the #4 baffle. I have trouble getting my oil to warm up enough. I had to put in a cockpit controlled butterfly valve in the opening, and even fully closed in the winter, I’m lucky to get up to 160*.
Also - my FF at 65% power (O-360, carb, fixed pitch) is 7.8 to 8 gph. Let me know if you need these drawings.
Click to expand...
Thanks Scott,

I'll ping you offline. Just left up there or I would have come by to grab them. I would love to get the plans from you, and will be back up later this month. I sure hope I can get this temp down, and I dream of the 8GPH days!

Thanks,
Eric
 
In case you're interested, you can get a complete set of drawings for the RV6 (or any model you want) on a USB stick from Van's for not much money. It will include all drawings, including optional ones.
 
Something that brought my CHTs down a bit was taping off half of my cabin heat air inlet behind cylinder 3. This was recommended to improve cabin heating by the desiger of the traditional RV cabin heat muff (Robbins). He said the 2" hole is too big (insert jokes) for RV speeds and there's excess ram air and to put aluminum tape over half. As a nice side-effect to taping off half, CHTs came down a little with definite improvement in cabin heating.
 
I have now added the front baffle and re-did all of the baffle seal, and RTV'd the heck out of everything. It was a bumpy day, so I couldn't run it as hard as I wanted, but.... It worked! Can't thank you all enough for the help!! I also added pressure pants during this time, and that also helped me pick up another 10 MPH or so.

CHT's were good, even on a hot take off, and my Oil stayed under 200.

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