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Oil Cooler issues

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wrongway john

Well Known Member
Oil Cooler & Pressure Issues

I bought this plane up north last year and really have been pleasantly suprised with it, but the TX heat issues are something I'd like to address. My oil temps are generally in the upper 180?s to lower 190?s in the summer , and I would like to get it into the 160?s if at all possible, to also help with better oil pressure as well. FWIW, I?ve got good compressions and low oil burn, perhaps one quart every 16-22hours, and CHT's are generally in the 330's-340's at cruise, so no problem there or even in climb out.

Looking at the pics, notice the small inlet for my oil cooler. It?s only 2.5?X3.5? (8.75? surface)opening going into the oil cooler which has a core of 4?X5.375? (21.5? surface).

From the pics, you can see there is almost no where to go. From this location, I might could raise it up another ?? and go in another ?? while still maintaining about a ?? from top of cowl, and a ?? of an inch from the motor mount. Cutting out this more of an opening would expose me to 12? of surface area, which might not be that much of an improvement.

What have other 6 owners done here? I?m open to any suggestions, and it would be greatly appreciated. Is 160's even obtainable in this TX heat without it being too much work?

John

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John, I think your oil temps are just about right, I wouldn't really mess with it at all. You at least want to get above 180?F on a flight so as to boil off any moisture that may be in your oil. I live in Florida so am familiar with the oil temp issues, but really, yours sound just right. If anything, just verify that the oil temp gauge is accurate. I think your goal of 160?F is way too low and probably not good for your engine, in my opinion. Also, plan so that you are able to achieve the 180?F desired temp in the winter months.

Just my .02 cents worth. :)
 
Thanks, all of you. But maybe you won't think it so good when I tell you about my oil pressure when it is that hot. When my oil temps get into the 190's, my oil pressure drops to about 60 at cruise. I’ve wrote down some numbers, and 10 minutes into flight, oil pressure is 77 and oil temp is 165. I’ve adjusted the vernatherm in two turns, hoping that would help both my oil pressure and oil temperature, but it seems the same. My A&P is going to order me another spring, since I've bottomed this one out, and also take a good look at the seal to see if that might need looking at.
 
wrongway john said:
Thanks, all of you. But maybe you won't think it so good when I tell you about my oil pressure when it is that hot. When my oil temps get into the 190's, my oil pressure drops to about 60 at cruise. I’ve wrote down some numbers, and 10 minutes into flight, oil pressure is 77 and oil temp is 165. I’ve adjusted the vernatherm in two turns, hoping that would help both my oil pressure and oil temperature, but it seems the same. My A&P is going to order me another spring, since I've bottomed this one out, and also take a good look at the seal to see if that might need looking at.
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Considering how much the cooler is blocked off, and how low your oil temp is in those conditions (compared to most other RV's), the first thing I would do is confirm the accuracy of your oil temp gauge.
Reduced oil pressure with hot oil is normal, and your 60 PSI is more than adequate, but it is very possible your oil temp is actually much higher that displayed.

BTW, it sounds like you are adjusting the oil pressure regulator, not the vernatherm (the vernatherm is not adjustable). If you have bottomed out on the pressure adjustment, I think you should definitely confirm the accuracy of your oil temp reading. I would bet the oil temp. is actually much higher than what is displayed.
 
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Okay, thanks, I?ll be more careful with my terminology. This is all still a bit new to me. I spent most of the first nine months learning to fly this thing, after not flying for 20 years, but now I need to start paying attention to this other stuff.

I do know right before sun up on my first start up of the day, my oil temperature matches the outside temperature. But I?ll have the A&P get another oil gauge to see if the 190?s is accurate or even higher.

In the summer I do nearly all of my flying in early morning or late evening. So with these measurements I've given here have been with me flying and the outside temperature in the eighties. I don't fly when it's around 100, I'm afraid to when I'm already getting these numbers.
 
John, a couple of things that you might consider. Where are you picking up your oil pressure? If you are using the normal port under the right engine mount, that would be about the highest reading. Further forward would give you lower readings. Also, I wouldn't be adjusting oil temps to fix an oil pressure problem; I would deal strictly with the oil pressure and resolve that first. The vernatherm probably is not going to have much affect, I think you must mean the pressure relief valve on top of the engine. If you have bottomed that out, then you are not bypassing any oil into the sump thus you have maxed out oil pressure for that particular oil pump. Also, Lycoming's spec for minimum oil pressure is 55 psi, so at least you are above that. Mine runs about 78 psi in cruise.

Just to make sure you are aware, the vernatherm fully seats at about 180°F forcing all of the oil through the oil cooler. Lower than 180°F, however, there's still quite a bit of oil going through your oil cooler--that's why in the winter sometimes it's necessary to block the oil cooler to raise oil temps. You would think that the oil is bypassing the oil cooler below 180°F, but some oil is always flowing through the oil cooler (as a safety measure). At 180°F, the vernatherm fully seats and forces the rest of the oil through the cooler. That's why you can sometimes see a slight drop in oil temp around 180°F when the vernatherm fully seats.

I would have your A&P hook up a direct gauge to your engine to see what pressures you're getting at the rear accessory housing and go from there. Perhaps you'll get some further recommendations here from the engine guys.

P.S. As I mentioned previously, calibrating your temp sender/gauge would probably be a good idea. One way to do this is to drop your sender into a small coffee can with water and boil the water with a torch... it should be close to 212°F at sea level of course.
 
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John, your oil temps are fine. The time to be concerned about the oil temp is if it hits 220+. Even 210 is acceptable here in the Texas heat. A stouter spring in the bypass may help fix the low oil pressure, also using Aeroshell W100 Plus straight weight oil may help too.
 
Pat, I?m not sure where I?m picking up on the oil pressure, but will look into it next weekend when I?m free again. Just have a little more time for today. If Lycoming is recommending 55 minimum, I suppose that is at cruise and the higher rpm?s. At idle, after landing, at 1,000 rpm?s, mine drops to 35 psi. If I pull all the way back to 800 rpm?s, it gets to 22-25, which if I remember reading right, Lycoming recommends 25 psi minimum at idle. I?ve noticed my manifold pressure is something like 11? at this time too after my landings at the lowest rpm setting on these hot days. Just as soon as I land, I slightly give it a bit more throttle to keep my alarms from going off, by keeping it at least around 900.

Something just doesn?t seem right, but not sure what direction to go in since it?s all new to me. Just looking at the oil cooler, and how little air was getting through I suspected it was the leading culprit for both my oil pressure and temps, but not sure any more after the feedback.


Neal@F14 said:
A stouter spring in the bypass may help fix the low oil pressure, also using Aeroshell W100 Plus straight weight oil may help too.
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Neal, that?s the oil I?ve been using, and logbooks also indicate that as well. Brian out at Kickapoo ordered me a stiffer spring that he said he would have for me next weekend. I?ll see if he still thinks it is worth a try.

Searching the archives, I?ve seen some who go with different settings for winter and summer.
 
John, I think you're on the right track, it will get sorted out. One thing to consider about the stouter spring (and I think it's worth a try) is that this is a pressure relief valve, so if you're not getting enough pressure to off-seat the ball and spring to begin with, then a stouter spring will do no good. I have also heard that a couple of washers under the spring is permissible. You can ask your A&P guy about that too. And if you're not getting 25 psi at idle, Lycoming says 25 psi minimum, so... I think further investigation is warranted. At idle, your pressure relief valve doesn't come into play, of course, because pressure is too low to off-seat the ball and spring... so worth investigating in my opinion. :)

What is your oil pressure at idle right after start-up when you know your oil temp is low? In other words, is there a difference in pressure at idle between the start and the end of the flight? I defer to the experts! Good luck. :)
 
wrongway john said:
I don't fly when it's around 100, I'm afraid to when I'm already getting these numbers.
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I went flying up here in Minnesota today, temperatures about 94, density altitude about 3200. Flew around the test area (I'm still in phase one). Flew at 3,000 feet -- 2,000 AGL -- and leaned it out to about 8 GPH...would change mixture to keep cylinder heads about 395.

EGT was about 1300...oil temp on a climb was about 204 or so and a slow cruise I could bring it down to about 195 or so.

And that was fine with me. Oil pressure was around 55-60 on the ground . I always wait until the temp hits 110 to fly and, yeah, it's about room temperature when I pull it out of the hangar.

None of those temps scare me a bit . Lycoming, I believe, says 245 if where you don't want to be.

Up around 4,000, the OAT was about 83 today and while pretty warm, the engine (an IO-360 M1B) didn't seem to be aggravated with me at all.

I don't think yours is trying to tell you anything nasty.
 
Pat Hatch said:
At idle, your pressure relief valve doesn't come into play, of course, because pressure is too low to off-seat the ball and spring... so worth investigating in my opinion.
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I honestly didn't know that, so thanks.

What is your oil pressure at idle right after start-up when you know your oil temp is low? In other words, is there a difference in pressure at idle between the start and the end of the flight? I defer to the experts! Good luck.
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Oh yes, big difference. This morning I wrote down a great deal of stuff. Outside temperature was 80 degrees. Oil temp was 80 degrees, and oil pressure was 99 then. End of flight, temps in 190's, idle at 800 rpms, 22 psi, at 1,000 about 35 psi.
 
If your oil pressure gets up to 99 psi, you need to back off on the relief valve. As stated before, the relief valve only regulates the max oil pressure. Until you reach that pressure, the relief valve doesn't come into play.
 
John, I think you can safely eliminate the pressure relief valve now as the culprit if you're getting 99 psi. It really looks to me like your next steps would be to back off on your pressure relief valve to make sure you don't exceed 95 psi on initial takeoff, and then calibrate your oil temp gauge to make sure it's indicating properly. After that and if your oil temp gauge checks out, "active surveillance" might be the operable strategy: Keep an eye on consumption, change your oil regularly, and cut the filter open to inspect for metal in the pleats. I'm not an A&P, but that's what I would do based on my experience.

Also, putting a manual (analog) pressure gauge directly on to the accessory gearbox port (as previously mentioned) for an engine run will serve to calibrate your oil pressure gauge on your instrument panel. Who knows, your oil pressure sender/gauge might be reading a little low as well.
 
Pat Hatch said:
John, I think you can safely eliminate the pressure relief valve now as the culprit if you're getting 99 psi.
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I believe so too now, thanks to you guys.

It really looks to me like your next steps would be to back off on your pressure relief valve to make sure you don't exceed 95 psi on initial takeoff, and then calibrate your oil temp gauge to make sure it's indicating properly.
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Took care of that this morning as well.

Thanks for you and others input on this. I just changed the title to this thread to "Oil Cooler and Pressure Issues" since we discussed both, and maybe others in future search engine searches with similar problems might find something to consider as well.

I just need to find a good A&P that is available and can go through it to find out what?s wrong. The one I got is currently having a hangar built, and after that he will be getting ready go to India for several weeks, so he may not have time for it any time soon. Hoping he can still make time, but I won't crowd him.

I did some more search engines on this oil pressure problem, and have found about 14 things that need to be checked thus far. Some of these low pressure problems are not too big of a deal at all, while others are, and could cause a healthy man a stroke! :eek:
 
oil cooler structure

From your picture, it does not look like you have an alum angle cross brace from the engine block to the cooler corner. There have been suggestions that additional support for the cooler is important. Look at other discussions on this point.
 
update

My A&P suggested moving the oil cooler to the front, he seemed to think this would be better. Took it up, 20-40 minutes into flight oil temps and pressure stabilized to these numbers:

Oil temperature 184 F degrees.
Oil pressure 71 psi at cruise, 23 squared.

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Outside air temperature was 86 degrees at cruise, so was just a little warmer than my first test. I’m surprised just a few degrees cooler in oil temp made this much difference in oil pressure. I’m roughly figuring for every degree in oil temp’ drop, it gave me about 1.5 more psi at cruise.

After landing, and 91 degrees outside temperature on ground, and throttle pulled all the way back, low oil pressure warning never went off, but still came down to 28 psi which wasn’t quite as good. Overall, I feel much better with these numbers though.

Other concerns: Oil pressure was 96 psi at last start up. My A&P discovered the spring was cut in half. When he put a full size one in, the oil pressure never got higher than 50 psi, so he put the cut off spring back in.

He talked to Skyranch, which said that could possibly be hiding bad main bearings or possibly a bad oil pump. Engine just barely has over 500 hours since overhaul, and hoping the bearings were put in new then, but overhaul can mean anything, and I don't have any paperwork to know what was done.

My oil was clean, and the magnetic screen on the oil filter hadn’t picked up anything either. He sent out my oil for analysis which might tell us something, but don’t have any previous oil analysis to go by.
 
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Oil Temp

I had an interesting flight this weekend. I normally cruise at WOT and then lean the old school method. EGT is around 1380 this way so I backed off the throttle about 1/4 inch as recomended on other post. It did lean out more because I had a 20 deg increase in oil temp! Went back to WOT, no change in mixture and the oil temp came back down to 190 as is my normal temp.

I was not expecting this and it was an eye opener until I figured out what I had done. This was my first flight after annual so I went into overdrive as to what had happened! What was the last thing I changed before the oil temp started to increase? The throttle position.

Good learning experience about leaning and oil temps.
 
We had a high oil temp, and also high CHT, in our RV6A. Just purchased. It has an O-320 with the same oil cooler installation as in your photo.

Oil temps were in the 230F range, and CHTs over 400.

I fixed it. I modified the cowl outflow, expanding it.

There was a badly-made strut in place that probably deformed under load, allowing the opening to close slightly. I replaced that with a better strut, slightly longer, and modified the plate that the strut rests on to get a better grip on the cowl. Now, the opening is about 1/2" lower.

I also took my dremel tool and cut the opening back 3/8".

So now we have a slightly larger opening, and it projects half an inch lower, acting slightly as a cowl flap.

Result -- about 40F reduction in CHTs, and 15F reduction in oil temp.

I haven't noticed any reduction in speed.

Dave
 
Dave, glad it worked for you. I guess there are several positions that work fine. I have also seen them on the firewall with a hose coming from where my hole was in my rear baffling wall then on to the oil cooler.

I finally took it up for a 102 degree day, and still no problems with oil temp 190 at cruise, and oil pressure 65. Never had taken it up when it had been that hot before.

My only regret is letting an A&P do it for me that I wasn't all that familiar with, and I let him talk me into doing it for me since he said I had all the parts there, and it was a quick fix, wouldn’t take no time at all. He ordered a lot of parts, and turned it into a three day job and that’s the hours he charged me for it at A&P rates. Claimed there was a lot more involved than what he anticipated. After having all of the cowling off, I noticed he left one spark plug wire resting against a head, and also had one of the oil hoses cutting into the fin of the oil cooler. I have since fixed those problems, otherwise, I think it would have eventually cut right into the oil hose given enough time.
 
There are also some oil cooler fin "wraps" you can apply directly to your oil filter - some are automotive, and some are aircraft, but they work well on my champ which sometimes gets hot here in Fla... they reduced my temp about 8 degrees or so and require nothing but a clamp at oil change time... solid state, and hey, every cooling fin helps a little. Best, Ed
 
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