What's new
Van's Air Force

Don't miss anything! Register now for full access to the definitive RV support community.

Fluctuating Oil Temp

D

Drippy

Well Known Member
Guys,

I have been fighting higher then desired oil temps on my IO540 equipped RV10. I tried to follow Tim Olson's baffle tighten up guidance and am running relatively good CHTs. In a 115kt climb my CHTs are hitting 380ish with #6, always the highest pushing 390-400 if I get a bit slow.

What I am seeing on my Advance Flight Engine Monitoring system is the Oil temp will climb up to 190-205F in the climb. But at cruise I tend to stabilize at 200-205F, but then will quickly roll down to 180-185F stay there for about 15-30 seconds then start to climb back to 200F. There doesn't seem to be a constant cycle to this temp change, but I notice it 3-5 times in a one hour flight.

I rebuilt the engine and did not replace the vertatherm and am thinking that replacing it is the next step. I did try a quick V/T check by flying the airplane until oil temp hit 200F then landed and did the hand temp check of the oil cooler and it was hot to the touch.

Before purchasing a $300 V/T thought I would ask if anyone has seen similar symptoms.

Mike Chase
RV10 50+ hours
 
I'd try some alternate temperature monitoring before replacing the vernatherm.

If you're interested, I may have a Rochester analog temperature gauge and sender you could bolt on temporarily to verify that what you're seeing is accurate. There might be someone more local to you with a similar sidelined gauge/sender.

Beyond that, you can pull the vernatherm and drop it in hot water and see what it does. Verify the water temperature with a cheap IR thermometer and see if the vernatherm opens the correct amount at 180F+. That's a fast way to diagnose the vernatherm without spending real $$. You can also look at the seat on the vernatherm while you have it out.
 
check water temp with a candy or meat thermometer. Everyone recommends checking the temp of everything nowadays without understanding emissivity. Water has a .96 emissivity at ambient temp. Chances are your IR gun is calibrated at .95 which is in the ballpark for most organic items. Not so good for bare aluminum. Some guns have adjustable emissivity settings, but even then it's an educated guess. This guide gives a decent baseline for different items.
http://http://www-eng.lbl.gov/~dw/projects/DW4229_LHC_detector_analysis/calculations/emissivity2.pdf
 
Drippy said:
Guys,

I have been fighting higher then desired oil temps on my IO540 equipped RV10. I tried to follow Tim Olson's baffle tighten up guidance and am running relatively good CHTs. In a 115kt climb my CHTs are hitting 380ish with #6, always the highest pushing 390-400 if I get a bit slow.

What I am seeing on my Advance Flight Engine Monitoring system is the Oil temp will climb up to 190-205F in the climb. But at cruise I tend to stabilize at 200-205F, but then will quickly roll down to 180-185F stay there for about 15-30 seconds then start to climb back to 200F. There doesn't seem to be a constant cycle to this temp change, but I notice it 3-5 times in a one hour flight.

I rebuilt the engine and did not replace the vertatherm and am thinking that replacing it is the next step. I did try a quick V/T check by flying the airplane until oil temp hit 200F then landed and did the hand temp check of the oil cooler and it was hot to the touch.

Before purchasing a $300 V/T thought I would ask if anyone has seen similar symptoms.

Mike Chase
RV10 50+ hours
Click to expand...

First, 205* is not something to be concerned with. Lycoming redline is 235 and most modern oil doesn't start to breakdown or oxidize until around 250-260.

In cruise does the oil temp stay at 200 or does it eventually go back down to 180-185?

Larry
 
cruise temps

thanks for the advice guys. I will verify the gauge and V/T.

In cruise it tends to stay around 200-205 I have seen it move up to 210 max on a climb in the summer on a 90+F day.

I have read the Lycoming 200-220F guidance but everyone else seems to be running sub 200F so wanted take a look.

I was thinking the V/T might be having a hard time staying closed and thus is cycling causing the temps to roll down then go back up when the oil cooler is being bypassed again.
 
We had an unstable oil temp at certain points during warmup and replaced the sending unit. The little bugger would red-X the oil temp at an artificially high reading. I knew it was wrong because there was no way the temp could get that high during warm up. Getting the sending unit out was a challenge, but well worth the hassle in the end.

-Marc
 
IO540

No I believe 200-220 with max 245F is what I read. Another RV10 at the airport and many on this post seem to run closer to 180F. So I was thinking I had some minor issues.
 
Drippy said:
thanks for the advice guys. I will verify the gauge and V/T.

In cruise it tends to stay around 200-205 I have seen it move up to 210 max on a climb in the summer on a 90+F day.

I have read the Lycoming 200-220F guidance but everyone else seems to be running sub 200F so wanted take a look.

I was thinking the V/T might be having a hard time staying closed and thus is cycling causing the temps to roll down then go back up when the oil cooler is being bypassed again.
Click to expand...

I don't think so on the issue of cycling. If you routinely run 200 in cruise and 210 in climb, The vernatherm should be fully extended or at least as extended and seated as good as it's going to get at the top of your climb and 210. It's unlikely that the 30 second drop to 180 is due to the vernatherm, which just prior was trying it's best to be closed.

What oil filter adapter do you have. I didn't pay attention to which model, but one of them has loose tolerences on the attach bolt holes and makes getting the V/T aligned with the hole difficult; leading to leakage at the V/T interface and therefore lower than normal cooling capacity.

200 is not that high and it is not likely that your V/T is shot, though they can fail incrementally. There is a simple test with hot water/oil and measuring the expansion of the end. This will rule in or out your V/T.

Larry
 
Last edited:
lr172 said:
What oil filter adapter do you have. I didn't pay attention to which model, but one of them has loose tolerences on the attach bolt holes and makes getting the V/T aligned with the hole difficult; leading to leakage at the V/T interface and therefore lower than normal cooling capacity.

Larry
Click to expand...

That was going to be my suggestion also. With the filter adapters it may be possible to get non concentric alignment. You should see a nice ?witness? mark all the way around the vernatherm where it?s seating, just be sure you?re not looking at old marks if this is a used vernatherm.
Also be aware the Casper Labs and B&C adapters each require a proprietary gasket. Not interchangeable.
Tim Andres
 
Just as a data point, in the summer I see 190-200in a climb. I climb at 25/25, 125-130kts. In summer temps, in cruise at 65-75% I see 180-185. In winter I typically have to completely close off the oil cooler.
 
Drippy said:
...at cruise I tend to stabilize at 200-205F, but then will quickly roll down to 180-185F stay there for about 15-30 seconds then start to climb back to 200F. There doesn't seem to be a constant cycle to this temp change, but I notice it 3-5 times in a one hour flight.
Click to expand...

Mine cycles about 10 degrees in cruise, 185 to 195. I have a theory, but it needs a test, and I can't get a particular plug out of the accessory case...
 
theory?

Sorry a bit slow what is the theory? I haven't made it to the airport in a few days (out of town) but am going to pull the V/T and see if the seat looks OK and them take it from there.
 
You must log in or register to reply here.
Back
Top