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Oil temperature question

CamTom12

CamTom12

Registered User
Huntsville, AL
Have you guys heard of any weird lycoming 4-cylinder situations that would make oil temps unusually high for all conditions? I have an O-320-160 that's giving me oil cooling problems.

CHTs are good (actually, they're very good. With some temporary cooling mods it was difficult to keep them all above 300 in 42 deg F OATs, oil temp was 185), engine runs smooth, makes good power, but oil temps are high (usually 220 or higher in cruise with ~55 deg F OATs. As the OATs go up, so does the oil temp). Oil pressure is great at ~80 psi at oil temps of about 220 deg F and below. Running XC 20w50 and a Champion oil filter on a Lycoming oil filter adapter.

Oil temp gauge and sender are checked good with the hot oil bath method, new vernatherm has been installed (the old one had a perfect circle witness mark on it which makes me think the seat is fine, though I didn't actually check the seat). Oil cooler is new as of 5 flights ago (meggit-troy 8406R).

First flight after the new oil cooler, oil temps were ~170 in 55 deg F OATs, now are back to being high (200-220 in ~40-50 deg F OATs)

Most folks I know are blocking their oil coolers off in similar OATs to try and get up to 180 deg F oil temps.

Any weird lycoming stuff you've seen in the past that I can check out? Next step I think I'm going to take the oil cooler lines to a local hydraulic shop to get inspected. My visual inspection with a flashlight didn't turn up any issues. What else should I look at?
 
Camtom
I followed you posts on the other page great job so far. Post a few pictures so people know what they are working on (not standard cub). I would try a vertical shield between #4 and the cooler with a scoop on top to direct air down the back of #4 cylinder. This will also help direct flow to cooler. Make the shield a two part affair so you can adjust the scoop up and down until you have the airflow right. I think you may have air just tumbling behind the cylinder and not flowing properly in that region. I would also keep the bottom of the cowl open as much as you can. I would run CHT'S at 310 all day long if I could.
DENNY
 
I would take a look at the vernatherm. Something may be making it malfunction and not allow sufficient oil into the cooler. Just a thought.
 
What's the motor story? Hot rodded? High compression? Anything that would tend to make higher than normal oil temps? Rear cooler? Why the new cooler started with normal temps and then morphed to high temps is curious. Have temps remained consistently high or do they vary? Are the baffles good? If the seals are a little short and blow out under pressure the oil temps would suffer.
 
phdigger123 said:
Sludge in the engine plugging the oil cooler?
Click to expand...

I was having high oil temps with my O-320 (150), 250 SMOH. Removed the old stock cooler and installed a Niagara Air Parts cooler. Oil temp with 80-85 degree oat indicates approximately 190. Plus, shed about two pounds off the nose which really helps while operating on floats. Cut open the old cooler and found heavy deposits of sludge. Gary
 
DENNY said:
Camtom
I followed you posts on the other page great job so far. Post a few pictures so people know what they are working on (not standard cub). I would try a vertical shield between #4 and the cooler with a scoop on top to direct air down the back of #4 cylinder. This will also help direct flow to cooler. Make the shield a two part affair so you can adjust the scoop up and down until you have the airflow right. I think you may have air just tumbling behind the cylinder and not flowing properly in that region. I would also keep the bottom of the cowl open as much as you can. I would run CHT'S at 310 all day long if I could.
DENNY
Click to expand...

Denny,
I'll put some pics up here in a bit and thanks for the kudos! I'll try that scoop idea to rule out airflow to the cooler. I've already determined that airflow to the engine is not an issue, but you're right- there might be something goofy going on back in that corner that's affecting the cooler itself. Technically speaking, airFLOW in the upper cowl shouldn't matter since it is stagnated by design to create high pressure, but stranger things have happened. My temp cowl openings were actually on the sides, cub style! They worked really well!

Dave Prizio said:
I would take a look at the vernatherm. Something may be making it malfunction and not allow sufficient oil into the cooler. Just a thought.
Click to expand...

Dave,
I installed a brand new vernatherm in accordance with a Lycoming SB and the symptoms didn't change. The old one had a full circle worn on its face, but I didn't check the seat or test either vernatherm so it's possible that the seat is bad or that both vernatherms are bad.

stewartb said:
What's the motor story? Hot rodded? High compression? Anything that would tend to make higher than normal oil temps? Rear cooler? Why the new cooler started with normal temps and then morphed to high temps is curious. Have temps remained consistently high or do they vary? Are the baffles good? If the seals are a little short and blow out under pressure the oil temps would suffer.
Click to expand...

Stewart,
Not hot rodded other than 160hp pistons. It's a wide deck motor. Temps remain consistently high. Yes, rear cooler, mounted on the baffles behind #4. The baffles are really good, they keep my CHTs way down. I experimented with some additional cooling mods (temporary) and got so much cooling air that I couldn't get the #1 CHT above 300 at 2475 rpm and leaned! Oil temps were 185, this was in 42 deg F OATs.

Cub@H20 said:
I was having high oil temps with my O-320 (150), 250 SMOH. Removed the old stock cooler and installed a Niagara Air Parts cooler. Oil temp with 80-85 degree oat indicates approximately 190. Plus, shed about two pounds off the nose which really helps while operating on floats. Cut open the old cooler and found heavy deposits of sludge. Gary
Click to expand...

I replaced my niagara 20002a with a meggitt-troy 8406R and other than the first flight where I saw really good oil temps, they have been consistently 10-15 degrees below where they were with the niagara. My engine has about the same amount of time on it, roughly 220 smoh.
 
Odd. My old 320/160hp had cool oil and warm CHTs. I used a Niagara 20003A on that plane. I'm concerned about oil temps on the new plane so it has two 20003As.
 
Gordon Misch said:
I'm betting something came loose to partially block oil flow in, to, or from the cooler?
Click to expand...

Any idea what to look for? The filter adapter feels tight and doesn't seem to move, though I'm going to give it a closer look when I get back to the plane now. I think anything else might be internal? Both cooler hoses are tight.
 
I had this problem and it was addressed by Randy Rubbert, a Lycoming engine guru from Reynolds ND. He really understands engines and he helped me address high oil temps on my 320-160 hp after my engine overhaul in which I had the cylinders ported and polished.

He feels that the rear oil cooler is a pretty poor design, particularly if you have (like me) an Airwolf remote oil filter hanging on the right firewall. He pointed out that if the timing isn't right it will run hotter than it should. We replaced all baffles with some sold by Roger Meggers in Baker MT. We ended up putting on a larger oil cooler and the combination of these things brought the temps down significantly.

Randy
 
WindOnHisNose said:
I had this problem and it was addressed by Randy Rubbert, a Lycoming engine guru from Reynolds ND. He really understands engines and he helped me address high oil temps on my 320-160 hp after my engine overhaul in which I had the cylinders ported and polished.

He feels that the rear oil cooler is a pretty poor design, particularly if you have (like me) an Airwolf remote oil filter hanging on the right firewall. He pointed out that if the timing isn't right it will run hotter than it should. We replaced all baffles with some sold by Roger Meggers in Baker MT. We ended up putting on a larger oil cooler and the combination of these things brought the temps down significantly.

Randy
Click to expand...

Randy,

I'm going to give lycoming a call next week, if they're stumped I'll try calling Randy.

I recently replaced my baffle seals with Macfarland rubber and upgraded my cooler to a higher quality one, though of the same size as I had.

Timing was checked at 25* during my last condition inspection at the end of June. Is that where yours is?
 
Check to make sure that someone did not put a cooler bypass plunger and spring in at some time. What is your oil pressure running?
DENNY
 
DENNY said:
Check to make sure that someone did not put a cooler bypass plunger and spring in at some time. What is your oil pressure running?
DENNY
Click to expand...

Denny, good idea - I'll check that for sure!

If oil temps are 220 or less I have about 80psi. When I've seen ~240 or so, oil pressure was much lower though still in the green.
 
DENNY said:
Check to make sure that someone did not put a cooler bypass plunger and spring in at some time. What is your oil pressure running?
DENNY
Click to expand...
That would make for cooler oil temps. I did just that and brought my oil temp. Down 15 deg
 
quote_icon.png
Originally Posted by Gordon Misch
I'm betting something came loose to partially block oil flow in, to, or from the cooler?



Any idea what to look for? The filter adapter feels tight and doesn't seem to move, though I'm going to give it a closer look when I get back to the plane now. I think anything else might be internal? Both cooler hoses are tight.
Click to expand...

I'm thinking possibly some rubber from a hose folding with the oil flow, or some sort of foreign material lodged in the cooler, or a piece of paper towel that could have been used to keep dirt out of the hoses stuck somewhere, or???? The vernatherm bypass plug seems possible, however the onset of high temps was sudden and associated with changing out the cooler. So it seems reasonable that something associated with disassembly / assembly could possibly be the culprit. Just one idea - - -
 
Last edited:
Gordon Misch said:
I'm thinking possibly some rubber from a hose folding with the oil flow, or some sort of foreign material lodged in the cooler, or a piece of paper towel that could have been used to keep dirt out of the hoses stuck somewhere, or???? The vernatherm bypass plug seems possible, however the onset of high temps was sudden and associated with changing out the cooler. So it seems reasonable that something associated with disassembly / assembly could possibly be the culprit. Just one idea - - -
Click to expand...

Gordon, good idea on the hoses - I'm going to take them to a local hydraulic shop and see if they can test/inspect them for me.

High oil temps have existed with this engine since I owned it. It wasn't so bad in cold temps (200-220 when leaned), similar to now. It's when it gets warm that oil temps get really hot, and keep me grounded and working on the airplane. The new oil cooler was an attempt to fix the high oil temps, and does make them marginally better, but not good enough that they'll be good in the summer.

The weird flight was the first one right after the oil cooler swap, which hap oil temps I would expect for the conditions (~170 in ~50 deg F OATs). Hasn't happened since. The only difference between that flight and the one before the oil cooler swap was the removal and reinstallation of the baffle section the oil cooler was installed on, the new oil cooler, and connecting the oil cooler hoses to the new cooler.
 
WindOnHisNose said:
He pointed out that if the timing isn't right it will run hotter than it should.
Randy
Click to expand...

That's what I was thinking. You haven't mentioned ignition, but if you are running an after market ignition system that rolls in some ignition advance, when you start getting that advance in cooler weather, the CHTs will stay cool, but the oil temps will run a bit warmer than you would normally see. I run Pmags on one of my Experimentals. I have warm oil temps above 5000' when all the advance gets rolled in regardless of the time of year.

I found the rear mounted oil cooler in my SC clone works quite well (using stock RV-7 baffling reinforced for the oil cooler weight), but I also opened up the side cheeks quite a bit to draw more air through behind the oil cooler.

-Cub Builder
 
Cub Builder said:
That's what I was thinking. You haven't mentioned ignition, but if you are running an after market ignition system that rolls in some ignition advance, when you start getting that advance in cooler weather, the CHTs will stay cool, but the oil temps will run a bit warmer than you would normally see. I run Pmags on one of my Experimentals. I have warm oil temps above 5000' when all the advance gets rolled in regardless of the time of year.

I found the rear mounted oil cooler in my SC clone works quite well (using stock RV-7 baffling reinforced for the oil cooler weight), but I also opened up the side cheeks quite a bit to draw more air through behind the oil cooler.

-Cub Builder
Click to expand...

I'm currently running a pair of Bendix mags timed at 25*. We checked timing at my last condition inspection at the end of June. I do have a pmag that I'm waiting to install until after I get the oil temp issues figured. My oil cooler is mounted on RV baffling as well. Good to know about your oil temps with the pmag, thanks!


Sent from my iPhone using Tapatalk
 
CamTom12 said:
Gordon, good idea on the hoses - I'm going to take them to a local hydraulic shop and see if they can test/inspect them for me.

High oil temps have existed with this engine since I owned it. It wasn't so bad in cold temps (200-220 when leaned), similar to now. It's when it gets warm that oil temps get really hot, and keep me grounded and working on the airplane. The new oil cooler was an attempt to fix the high oil temps, and does make them marginally better, but not good enough that they'll be good in the summer.

The weird flight was the first one right after the oil cooler swap, which hap oil temps I would expect for the conditions (~170 in ~50 deg F OATs). Hasn't happened since. The only difference between that flight and the one before the oil cooler swap was the removal and reinstallation of the baffle section the oil cooler was installed on, the new oil cooler, and connecting the oil cooler hoses to the new cooler.
Click to expand...

Your symptoms still sound to me like sludge in the engine plugged up the new oil cooler. First flight was good and it got blocked with sludge so subsequent flights have high oil temperature. I would remove the cooler and backflush it with solvent and see what comes out. If the oil cooler worked on the first flight, it should have continued to work, unless the flow of oil or air was blocked. From what I read, the air flow is not blocked, so it only leaves a blocked oil flow as the culprit.
 
I have been fighting high oil temps for 3 years on my 160 cub. So far no silver bullets but getting rid of the vernatherm seems to have done the most good.
 
Differential tester was all high 70's. I'm going to try an automotive tester when I get back home


Sent from my iPhone using Tapatalk
 
Is it possible two hoses were reversed accidenally thus changing the direction of oil flow through the oil cooler or? I recall a Mack engine that tried to burn itself up after an overhaul. The heater hoses were reversed and that pressurized the thermostat after its first heat cycle following cold start up. Some things don't like to be fed backwards. jrh
 
Jrh,

I'm no expert on these engines, but I don't know if that's possible on the O-320 series.

Here's a link to the Lycoming troubleshooting guide with an oil flow diagram: http://www.yeeles.com/Reference/Hi-Temps.pdf

My lines are routed IAW fig 4.

I have also checked everything in this document except the last paragraph. Last night I opened a temporary hole in the low pressure side of the cowling right behind the oil cooler to rule out a local high pressure back there. If that doesn't work, I'm going to pull the hoses to have them inspected at a local hydraulic shop and start working down the rest of the suggestions in this thread. Thanks to everyone that's made a recommendation so far and please make more as you think of them- this is a wonderful airplane and tons of fun to fly. I'm hoping I can get this fixed soon and just go flying for fun some more!
 
I opened up another temporary lower cowl exit (but this time right near the oil cooler) and got between 3.8 and 4.3" pressure differential between the upper and lower cowl on tonight's flight. Saw oil temps around 185-190 with OATs around 50 deg.

Settled into a long 2200 rpm descent (500 fpm) and after temps stabilized I saw CHTs from 270 to 305 and oil temp stayed at 185-195. That would make some sense if the vernatherm was doing its job.

Then as I continued the descent with no changes to the throttle/mixture and OATs rose as high as 70 deg, the oil temp started rising and got up to ~200.

I think I will work on opening the lower cowl as well, but it's probably a combination airflow and oil something.

Nice to rule out any weird local airflow issues in the lower cowl. Oil change is coming up soon, and when it does the hoses will come off and go out for inspection and the oil filter adapter will come off for inspection/new gasket. The oil cooler will get flushed with solvent.

The oil will go out for analysis, and the vernatherm will get tested for proper extension.

I'll give Lycoming/Randy a call before I start tearing into things. Would have done it before today's flight but I didn't have a chance. Took the plane to the fam for the holidays since the OATs are cool and it's an opportunity to put more hours on the oil before I swap it.
 
You may still want to consider getting rid of the vernatherm. I was urged to do it by my engine builder on our 195 first and now have done it on our 160 cub.
 
Rice farmer said:
You may still want to consider getting rid of the vernatherm. I was urged to do it by my engine builder on our 195 first and now have done it on our 160 cub.
Click to expand...

I've read that Vetterman put the bypass plug back in his RV, removed the vernatherm, and regulates oil temps through oil flow control to the oil cooler by way of a ball valve controlled in the cockpit. Honestly something that I wouldn't mind doing (I actually enjoy full-manual operations in my hobbies, I like to adjust things and be involved in the operation).

I'll keep this in mind. How does yours work, is it like this?
 
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