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High Oil Temp

jtate747

Member
My oil temperature has been increasing over the last few months. In an effort to troubleshoot, I have operated in harsh conditions to check temp accuracy, oil cooler in/out temps when high, etc. Harsh meaning afternoon flights (103°F, full power)
Details: RV-6A, O-360, constant speed prop
I have checked the following:
- Baffles - all appear to seal very well
- Oil Temp accuracy- checked sump at 240°F, after shutting down at 241°F
- Vernatherm (boiled in H2O..... opened at 184-188°F
- upgraded from 7 row cooler to 9 row cooler
- changed ducting from 3” to 4”

It takes about 15-20 minutes to reach 245°F with OAT of 103°F.

My thoughts are
(A) vernatherm expands ok, but not seating right- restricting flow
(B) timing haven’t checked that, but a friend mentioned that today
(C) outflow duct. Right now the oil cooler is open on bottom side. Another friend said to duct the flow out of engine compartment into stream for “suction”

Any help would be appreciated.
 
Have you noticed a recent increase in debris load when you cut open you filters or in the sump screen? The cooler is upstream of the oil filter and can capture large debris, like carbon chunks from engines that burn a good amount of oil.

How far did nthe vernatherm expand. You need to measure the distance that it expands at 190* There is a spec out there; I don't remember it. They often fail by not fully expanding (this prevents a portion of the oil from going to the cooler). Also check the tapered end of the vernatherm for wear. Also check the seat that the vernatherm tip seals against for wear. Wear in this area is common enough that Lyc has an SI for repairing it.

Do you have an ECI oil filter housing that was removed recently?

Larry
 
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SNIP

How far did the vernatherm expand. You need to measure the distance that it expands at 190* There is a spec out there; I don't remember it. SNIP
Larry

DanH kindly posted the specs in this thread. See post #26. See also the graph I posted of my vernatherm extension vs temperature in this thread, post #13.
 
My oil temperature has been increasing over the last few months. In an effort to troubleshoot, I have operated in harsh conditions to check temp accuracy, oil cooler in/out temps when high, etc. Harsh meaning afternoon flights (103°F, full power)
Details: RV-6A, O-360, constant speed prop
I have checked the following:
- Baffles - all appear to seal very well
- Oil Temp accuracy- checked sump at 240°F, after shutting down at 241°F
- Vernatherm (boiled in H2O..... opened at 184-188°F
- upgraded from 7 row cooler to 9 row cooler
- changed ducting from 3” to 4”

It takes about 15-20 minutes to reach 245°F with OAT of 103°F.

My thoughts are
(A) vernatherm expands ok, but not seating right- restricting flow
(B) timing haven’t checked that, but a friend mentioned that today
(C) outflow duct. Right now the oil cooler is open on bottom side. Another friend said to duct the flow out of engine compartment into stream for “suction”

Any help would be appreciated.

I will be interested in your findings or possibly team up in the research considering we are in the same area.
I have also been aiming to lower my oil temp, though no where near where you are. I just checked the accuracy of my oil temp probe which was spot on, within 1-2 degree F, but when I check the oil temp from the sump, it is fair amount lower then what the probe is reporting.

Mine gets to around 200F during the cruise in the afternoons of Sacramento area but I like to lower it if I can.
 
I see that this is your 12th post. Is this a new engine on a new airframe? How many hours total time on the airframe and engine? What engine? What oil cooler are you using? Where is the oil cooler mounted?

First thing is calibrate the oil temperature transducer. Instrumentation errors can have one chase a problem that do not exist.

New and or rebuilt engines will have higher temperatures.

Ignition timing set too far advanced can make high CHT and oil temperatures higher than correctly set ignition timing.
 
I measured a 0.160 increase when heating. I heated to about 200°. Maybe it is not fully extending, allowing oil to flow in parallel, both to the cooler and internally. That would explain why temps are hot on both sides of cooler and in sump as well.

I did cut open the oil filter, but found No debris or metal. I also sent in oil to Blackstone 2 weeks ago, but no results yet. As of yesterday, they still had not received it.

I did not mention it earlier, but when the oil temps are rising, the CHT’s are around 360-380. As the oil gets hotter, these will follow, but still haven’t seen them much higher than that.. I chicken out when the oil reaches about 244° and start to richen it up, pull some power & keep speed up. I don’t like my lubricant breaking down on me!

The engine has about 130 hours on it SMOH, but sat for about 8 years (in AZ). Came from a Mooney whose wing was shredded by a pilotless plane. Pilot caught up with plane after shredding occurred.

I installed an Aero Classics 9 row cooler (8000074 from Spruce). I am confident the oil temp is accurate. Have checked in numerous areas with both a remote thermometer and an IR gun. Engine is definitely hot.
 
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Was oil temperature ever good?
Where is the oil cooler mounted?
How long is the SCAT going to the oil cooler?
How much of a BEND do you have in the SCAT between baffle and oil cooler?
(Trying to figure out if there is too much restriction to airflow getting to the oil cooler.)

I had issues with a firewall mounted oil cooler during Phase I flight testing (22-years ago/September 1997) in SoCAL. Moving oil cooler to baffle behind cylinder #4 fixed all my oil temperature issues. I only had 3" scat tubing when mounted on firewall. 3" SCAT is only 7 square inches of opening. 4" SCAT is 12.5 square inches. Moving to the rear baffle, I then had 3 X 5 = 15 square inches. (Area of Circle = Pi times Radius Squared)

BTW, with hot engine and hot ambient temperatures, I will typically have highest CHT at 390 in cruise. Typically oil temp is between 190 and 210. Yes after a hot refuel with quick turn and full power climb, I almost never see above 220 oil temperature. I did calibrate my oil temperature probe by placing it in an oil filled tin can, heating it with a propane torch, measuring temperature with a candy thermometer, and comparing it to engine monitor oil temperature while still connected to aircraft wiring.

High oil temp can be cause by lots of things including ignition timing. Ignition timing set too far before top dead center can raise CHT a lot. I recently did the 500 hour mag inspection and put everything back together on the ground with timing too advance. I saw 350 CHT before I ever took off. Knew something was wrong and was able to find incorrect ignition timing when I checked.
 
Option

Wrap the exhaust pipes with fiberglass tape to reduce the heat transfer to the air downstream of the oil cooler/ lower chamber, available through Amazon/auto stores.
 
On top of the info Gary has requested, pictures of the baffles, oil cooler installation, and cowling exit would help better understand the problem.
 
Caution if you wrap your exhaust pipes.
Variable advice. Exhaust manufactures do not support wraps. Even coatings get debated, but please show ANYONE fabbing aircraft exhaust supporting wraps.
 
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Do NOT wrap your exhaust pipes.

Poor advice. Exhaust manufactures do not support wraps. Even coatings get debated, but please show ANYONE fabbing aircraft exhaust supporting wraps.

I am most likely the only person that supports exhaust wraps. 22-years and 3,400+ flying hours and I like the result exhaust wrap has given to my aircraft. In my 22-years and 3,400 hours of experience using exhaust wrap, reduced under cowl temperatures are worth the expense of a new exhaust system every several thousand hours of operation.

Just my opinion and your results may vary.
 
Is this John from Lincoln? Hangared on the south side?


My oil temperature has been increasing over the last few months. In an effort to troubleshoot, I have operated in harsh conditions to check temp accuracy, oil cooler in/out temps when high, etc. Harsh meaning afternoon flights (103°F, full power)
Details: RV-6A, O-360, constant speed prop
I have checked the following:
- Baffles - all appear to seal very well
- Oil Temp accuracy- checked sump at 240°F, after shutting down at 241°F
- Vernatherm (boiled in H2O..... opened at 184-188°F
- upgraded from 7 row cooler to 9 row cooler
- changed ducting from 3” to 4”

It takes about 15-20 minutes to reach 245°F with OAT of 103°F.

My thoughts are
(A) vernatherm expands ok, but not seating right- restricting flow
(B) timing haven’t checked that, but a friend mentioned that today
(C) outflow duct. Right now the oil cooler is open on bottom side. Another friend said to duct the flow out of engine compartment into stream for “suction”

Any help would be appreciated.
 
Cool, good data point.

What type steel? 321 or ? Who fabbed them?

Have seen flange weld cracks failures with and without wrap.

Where do you start the wrap from the flange weld?

Do you remove the wrap to inspect and replace annually or xx hours?

Wraps DO definitely lower under cowl temps. I bet it drops oil temps 5 to 10 degrees if rear baffle mount, unducted cooler is used.
 
Wraps DO definitely lower under cowl temps. I bet it drops oil temps 5 to 10 degrees if rear baffle mount, unducted cooler is used.

A exhaust wrap should reduce lower cowl plenum air temperature, and reduce radiant heating of adjacent components.

The first is mostly useless, except for those who have a vapor lock problem, and there are better ways to address it.

Reduced radiant heating can be useful. Two examples; a red cube in the fuel line between the pump and the carb or fuel control, or reduced heating of the intake pipes. Heat shields are the alternate plan.

Exhaust wrap is not going to reduce oil temperature, unless radiant heating is real bad from pipes in immediate proximity to the oil sump.

Break.

Forget ducting the oil cooler exit air to the cowl exit for "suction", at least until you measure your lower cowl plenum pressure. Given a stock cowl, it probably quite low.

Break.

Blowby is a subtle but very powerful driver of oil temperature. Consider the effect of hot combustion gas leaking into the crankcase space. If the usual punch list doesn't cure the problem, take a hard look at leakdown, bore clearances, and cylinder wall condition.
 
High oil temps

I had exactly the same problem as you. I have an I0360 A1-B6. My oil temps were getting in excess of 225 at ambient of 86-90 degrees. I did all the same tests and got the same results. Took out the vernatherm and tested it....... opening at the proper temp and opening .240 inches at 200 degrees in boiling water. I bought a new vernatherm only because mine had 850 hours on it. Got the new one and tested it in the hot water........ guess what ????? Exactly the same results as the old one ! I installed the new one into the plane and test flew on a 86 degree day. My oil temps stabilized at 215 degrees. I can't explain the vernatherm test results. At any rate, the new valve got my operating temps back in the green and I'm happy. BTW..... the best price for the vernatherm was at Air Power in Dallas http://www.airpowerinc.com/productcart/pc/prodparts.asp?catid=1&subcat=108&mfgid=TL&prodid=12708.

Good luck
 
Exhaust pipe wrap

The Exhaust wrap not only cuts down radiant heat transfer, but convective air temps in the lower cowling chamber (less air expansion) which helps more airflow through the oil cooler and baffles. May reduce cooling drag? On the negative side the EGT’s run ~100*F hotter which creates higher exhaust pressure during valve overlap (lower VE?). My testing was ~5*F oil temp reduction and no measurable speed impact....
 
Please see my post on RV-7/7A. . . search "Showplanes" and "Louvers" in separate posts. I'm very happy with my new lower CHT's & OT !
 
- Yes, John from KLHM.
- Scat changed from 3” to 4” (About 12” long with 1 90° bend)
- I am the 3rd builder, & the original oil cooler was already installed. After Studying numerous drawings, came to conclusion It was plummet wrong by a previous builder. I moved the line out to the oil cooler to the port just below the oil filter. It was on the plunger port on top. I capped off that port. The line from oil cooler back to the engine was correct.
- Test flew again yesterday thinking I was going to have the coolest oil in an RV...... no luck.
- Today will install a used Vernatherm I picked up the other day to see if anything changes.....

Related.... I need to get a Picassa or Dropbox acct in order to show pics. Will do that later today or tomorrow as a pic tells far more of the story.
 
I picked up a slightly used Vernatherm 53E22144 (Looked almost new), tested it & hoped for better results. Installed yesterday, flew in the evening 85° out & same results. This Vernatherm seemed to open a little more than original in hot water:
Temp. Movement
Cold. 0
160°F. 0.031
170°F. 0.032
180°F. 0.131
190°F. 0.211
200°F. 0.266

I did post the pictures of the installation here: https://www.icloud.com/iclouddrive/096WWl6xw0h4TCzLRnluXMFkg#Oil_Temp
 
OIL TEMPS

OIL COOLER INLET VENTURI.jpg
Assuming you have a sharp edge on the inlet at the rear baffle, I had the same problem. Changing from 3" diameter SCAT to 3" diameter SCEET (smooth bore) and adding this inlet with a 3/4" inlet radius lowered my temps 15 deg F.
 
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