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Continuing Problems with Oil Temps

lr172

Well Known Member
I have an IO-320 6A. The oil cooler is a Mocal 10 row (same as Setrab and heard several reports of success with 7 row version) mounted on the baffle behind #4. Hoses are new; replaced this spring, -6 size.

I had goods success last fall, with temps remaining in the 190 range even in 90* ambient days. This spring I noticed higher temps reaching max's of 220-225 at 75% power levels. I have replaced the cooler, as I thought it may have become blocked with all the carbon I had in the oil during break-in (due to a glazed cylinder). I have two different verhatherms that I have tried (neither new). The one I flew with today was tested last night. I put it in 190* water and observed a growth of .230" I saw Dan's post and his tested at .248" The minimum is .160 or .180. It would seem that the Vernatherm is working properly.

I don't really know where to go next. I can't see in the vernatherm cavity and I have considered removing the oil filter housing (lycoming style with V/T pointing down) and replacing with screen to rule out issues with the bore that the vernatherm seals. I think that I also have a spring and plug laying around to bypass the vernatherm all together. I have also considered buying a new vernatherm.

Does anyone have suggestions or seen similar problems they could share insight from?

Thanks,

Larry
 
I'm sure others will jump in here but the first thing that catches my eye is the #6 hose size. Thats pushing it as far as Im concerned. And if you throw in a couple of 90 degree fittings, it makes it worse. Might explore running the #8 hose, keeping it as short as possible, and 45 or 180 degree fittings wherever you can.
 
I'm sure others will jump in here but the first thing that catches my eye is the #6 hose size. Thats pushing it as far as Im concerned. And if you throw in a couple of 90 degree fittings, it makes it worse. Might explore running the #8 hose, keeping it as short as possible, and 45 or 180 degree fittings wherever you can.

Thanks Michael. There is one straight fitting, two 45's and one 90. All are hose fittings, so a generous radius. I have read quite a few posts on the the subject of -6 lines and it seems the flow is adequate, but could increase pressure. It was my understanding that many engines, including certified, run these lines. I also had good success with this, even during the high heat of break-in. I realize that 8's are better, but it worked for me last fall

Larry
 
Let's see a few under-cowl pictures:

1) Your baffles and seals.
2) The intake area for your cooler.
3) The exit area for your cooler.

On my -6, I originally undersized the hole in the baffles for the baffle mounted cooler. After 6 months (?) of fighting oil temperatures, I opened the hole up as large as I thought practical, which gave immediate benefit.
 
Hoese to/from the cooler really should be -8. You would be really surprised if you looked at the flow rates of the oil pump. In a typical Lycoming the complete oil quantity is sometimes cycled in a minute.
Sure there are a lot of other factors, but choking it down to start with is not helping. What works in certified airplanes is not always transferable in our very-tightly-cowled engines. :)

Vic
 
Let's see a few under-cowl pictures:

1) Your baffles and seals.
2) The intake area for your cooler.
3) The exit area for your cooler.

On my -6, I originally undersized the hole in the baffles for the baffle mounted cooler. After 6 months (?) of fighting oil temperatures, I opened the hole up as large as I thought practical, which gave immediate benefit.

I'll take a couple of pics. I forgot to mention that I think my baffles are in decent shape. My CHT's run 340 with #2 at 360* at 75% power. I stay under 400 even in hard climbs. My cut-out for my cooler fully matches the size of the cooler and the bottom of the opening sits just above the fins of #4, so not blocked by the cylinder. Area behind the cooler is wide open and not obstructed.

Larry
 
I am trying to install the plunger and spring to force everything to the cooler. That should help me troubleshoot the verntatherm / housing and confirm I am cooling as I should with my cooler and hoses.

I have a plunger, but I am not sure I have the right spring. Does anyone have the relaxed length of the 69436 spring used with this plunger? The one that I have sits proud of the top of the threaded opening by a good 1 1/2" It makes me suspect that is is the correct spring.

Larry
 
Try easy things first, even if unlikely. Pull your temperature probe, provide a ground, and hold it in boiling water. What does it read?
 
Try easy things first, even if unlikely. Pull your temperature probe, provide a ground, and hold it in boiling water. What does it read?

A Good idea. I did that during my initial troubleshooting. It read within a few degrees of a quality thermometer at 200* It also mirrors ambient temps closely on cold startup.
 
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Correction

So I just received an email from a very trusted friend who tells me that they did some testing on the early RV-4's and found they could RAISE the oil temps by using larger lines and that using smaller lines actually made the oil cool better.
I would never have guessed that.

Vic
 
So I just received an email from a very trusted friend who tells me that they did some testing on the early RV-4's and found they could RAISE the oil temps by using larger lines and that using smaller lines actually made the oil cool better.
I would never have guessed that.

Vic

I wouldn't have guessed that, but not really surprised. The little that I have researched on the subject indicates that if you pass the fluid through too quickly it can't give up the heat potential afforded by the cooler design. I believe it is a balance of many factors with exposure time one of them. I would have expected this to be engineered into the passage sizes of the cooler though.

With a more free flowing cooler design, I could see how a smaller line would slow down the flow a bit and increase exposure time, therefore increasing heat rejection.

Larry
 
Let's see a few under-cowl pictures:

1) Your baffles and seals.
2) The intake area for your cooler.
3) The exit area for your cooler.

On my -6, I originally undersized the hole in the baffles for the baffle mounted cooler. After 6 months (?) of fighting oil temperatures, I opened the hole up as large as I thought practical, which gave immediate benefit.


Here are a couple of shots of the cooler, front and back:

2zqedtv.jpg

igzvhf.jpg


Larry
 
High efficiency cooler

Looking at the fins on your cooler, I'm struck by how few of them there are when you compare it to the Aero Classics HE series coolers. We have a Niagara on our O-320 6A that is marginal - and it looks to have closer spacing than yours, though not as close as the HE series coolers.

+ 1 for #8 hoses. And look into a more efficient cooler. Call Wayne at Pacific Oil Coolers. Maybe he's got something better that would fit into the space you've got.

Ed
 
I agree on the cooler looking a little weak. It looks more like a radiator we use for the Rotax engines rather than an Oil cooler for Lycomings.

Vic
 
So what changed from the low oil temps to the higher temps? Hoses? or hoses, and cooler?
If you had the same -6 hoses as the earlier install, and low temps, and thats all that was changed, then I'd do some checking on the liners.
IF the cooler was also changed, then we are throwing multiple parts at a changed problem----cooler, hoses AND the install, Air leaks around the cooler,
etc.
I'd take a step back and look at things.

Tom
 
Hoses are new; replaced this spring, -6 size.

I had goods success last fall, with temps remaining in the 190 range even in 90* ambient days. This spring I noticed higher temps reaching max's of 220-225 at 75% power levels.

Ummmm. So what kind of hoses were on it when it was running cool?
 
Are the hoses home-fabricated? Are you sure the fittings are installed correctly with no "flap" of cut hose blocking the flow?

Vic
 
Ummmm. So what kind of hoses were on it when it was running cool?

Installation is identical to last fall. When I installed the FI system this spring, I replaced the -6 hoses with a higher quality hose and fittings for safety and reliability. It is possible there is something wrong with the hoses and will check later. It is possible this started before that event, the weather was cold; couldn't get to 220 with no cooler installed.

Larry
 
So what changed from the low oil temps to the higher temps? Hoses? or hoses, and cooler?
If you had the same -6 hoses as the earlier install, and low temps, and thats all that was changed, then I'd do some checking on the liners.
IF the cooler was also changed, then we are throwing multiple parts at a changed problem----cooler, hoses AND the install, Air leaks around the cooler,
etc.
I'd take a step back and look at things.

Tom

The only thing that changed was the hoses, but I can't confirm that it wasn't compromised before that event as ambients were below 40* The cooler was replaced as my third step (after vernatherm swap and sensor check) in troubleshooting this problem.

Larry
 
Are the hoses home-fabricated? Are you sure the fittings are installed correctly with no "flap" of cut hose blocking the flow?

Vic

It is possible; they are home-made (I have made many). I thought I checked for flaps on each hose, but mistakes are certainly possible. They are the type of fitting where the tip is in the rubber before thread engagement and I always use oil. The tip is small and rounded. It goes in very easy and seems it would be difficult to cut a flap of rubber.

I flowed each with water after assembly and had a strong and expected stream of water on the exit end (both directions) on each hose.

Larry
 
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I got the plunger installed last night. I will take it up for a flight this afternoon. That should give me a good direction on where to go next.

Thanks for all of the ideas and assistance.

Larry
 
They look like aftermarket 701 hose, and it is a probably that there is a restricted flap at the liner. I'd scope the hose to verify if there is a a flap in it.
Tom
 
They look like aftermarket 701 hose, and it is a probably that there is a restricted flap at the liner. I'd scope the hose to verify if there is a a flap in it.
Tom

Tom,

It is Aeroquip hose (FCP06100). Am I looking for a flap at the end where the fitting is installed or are you suggesting that there could be a flap anywhere along the length of the hose?

Larry
 
Installation is identical to last fall. When I installed the FI system this spring, I replaced the -6 hoses with a higher quality hose and fittings for safety and reliability. It is possible there is something wrong with the hoses and will check later. It is possible this started before that event, the weather was cold; couldn't get to 220 with no cooler installed.

Larry

So you installed a new fuel injection system also about the time that this started?
 
Larry, a flap piece of the rubber liner thats made when the stem is screwed into the hose. Sometimes it cuts the liner and leaves a hanging chad:eek:.
Tom
 
Ok. Plunger in, theoretically forcing all oil through the cooler. Did 30 minutes at 75* ambient (at my altitude) and 75% power. Temp maxed around 210. Much better than with the second V/T, which was 230* However, yesterday's test on the first V/T gave me about the same temps, but I didn't push it long enough to know if it topped out there or would have kept going.

As with my first rounding of troubleshooting, things seem to point to a cooling capacity issue. Tomorrow I will pull both hoses and check for any blockages. Cooler is brand new, so running out of steps after the hoses. Did anyone see problems with the cooler installation? Anything else that I am missing?

Larry
 
Cooler is brand new,

Larry

OK, new cooler.

How were the temps before installing the new cooler?

OK, re-read you first post-------did you replace both the lines and cooler at the same time?

Did you do anything else to the plane between last fall and this spring??
 
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Ok. My memory fails me again. I went through a few old logs from last fall (only had a two before cooler weather). I had a few occasions with temps max'ing in the 215 range, similar to what I am getting now. Surprisingly though, I had one run with more power than the others - 2600 RPM vs. 2400/2500 RPM and the temps stabilized around 195; similar ambient. Obviously the airspeed was higher. I am wondering if there is some type of airflow problem. Or possibly too small of a cooler that gets better with more airflow.

In summary, it seems that V/T #2 isn't working well, but with V/T #1 or plunger is netting me max temps in the 210-215 range. Given what I just learned, I will likely find the hoses fine, but will check. This leaves me cooler capacity.

I could either buy a larger cooler or work on the airflow through my current cooler. I have done a bit of research tonight, but will need more. Any pearls of wisdom on my setup to improve cooling? I have considered a defelctor on top of the #4 fins, to separate air for the cooler, but it would seem I should have enough based upon similar setups working.

It appears my cooler is rated to reject 7500 BTUs/Hr or 125 BTUs/Min. Does anyone know what an IO-320 (160 HP) requires?

Larry
 
Do you have BOTH the vernatherm and the plunger installed at the same time? I think only one of them should be installed at a time.

Vic
 
Do you have BOTH the vernatherm and the plunger installed at the same time? I think only one of them should be installed at a time.

Vic

I do. I have the Lyc oil filter adapter, so the V/T seats in that housing and not the hole on the face of the accy case (therefore no mechanical interference w/plunger & spring) The V/T and the plunger essentially do the same thing - they block the flow of oil into the oil filter, forcing it to follow the alternate exit in the primary oil pump feed gallery, which is the feed into the oil cooler. The plunger is just doing it upstream of the V/T. The cooler return line goes to a different chamber of the housing (no V/T interaction) and on to the filter/engine. There may be some negative consequences of having two spring loaded devices to bypass oil if the cooler plugs, but I only did this as a test to isolate my problem and will be removing the plunger or the V/T after testing.

Larry

Larry
 
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Larry has it right. Having both the VT and the viscosity valve plunger installed won't make any difference with the AC-style Lycoming filter adapter.
 
different hoses?

I'm wondering if the new hoses, if a different brand/style, might just have a smaller I.D. for the same nominal hose size, because of a different liner. The -6 hose may already be a little marginal, and then, a different brand with a smaller I.D. would be noticeably worse.

I would still consider switching to -8 hoses.


There are very noticeable differences in performance of different brands of coolers. Others noted that this one is a a bit light on cooling fins. If/When you switch coolers again, go with a real Steward-Warner style cooler. The Niagra's seem to be "OK" but not as good as the S-W.
 
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I'm wondering if the new hoses, if a different brand/style, might just have a smaller I.D. for the same nominal hose size, because of a different liner. The -6 hose may already be a little marginal, and then, a different brand with a smaller I.D. would be noticeably worse.

I would still consider switching to -8 hoses.


There are very noticeable differences in performance of different brands of coolers. Others noted that this one is a a bit light on cooling fins. If/When you switch coolers again, go with a real Steward-Warner style cooler. The Niagra's seem to be "OK" but not as good as the S-W.

Good points and ideas here. I had been clinging to the hope my cooler was adequate and didn't want to buy another cooler and fab up a new mounting if avoidable. Seems the capacity is just not there. I agree that the hoses may be contributing some, but I am getting 215 when I want 190. My next course will probably be a cooler and will get -8 lines when I do that. My Mocal as tne AN flare fittings, so need new cooler to swap to -8's.

I have a used SW 8406 cooler. I had struggled to get all of the crud out if it, but now thinking I'll flush it a again and try it. It sits upstream of the filter, so if there is a bit of debris left, it will get caught by the filter.

I am still hoping others may offer ideas to improve the airflow through my current filter to improve performance. Does consolidating adn directing the exit air from the cooler help?

Larry
 
I am still hoping others may offer ideas to improve the airflow through my current filter to improve performance. Does consolidating adn directing the exit air from the cooler help?

Consolidating and directing, no. What matters is pressure at the exit side. A duct can be used to port the exit to a region of lower pressure. If increased pressure delta provides more gain then the frictional duct losses subtract, the result should be more mass flow.

 
exit diffuser

I don't think you gain much from any kind of splitter that shields the flow into the cooler from the flow into the cylinders. That flow has not picked up very much heat yet.

The cooler is just exhausting into a 'plenum', the open space behind the engine baffles, so the cooler exit pressure matches the local pressure there.
A well-shaped diffuser duct on the cooler exit would make the pressure at the diffuser exit match the local pressure, thus the pressure at the cooler exit is lower, and air velocity higher.

BUT....

The space you have to work with is limited, and it is easy to make a poor diffuser. You could give it a try if you want. I would make a short diffuser, maybe 3" or 4" long, with about a 10-degree angle. In case you are unfamiliar, the diffuser duct is just a short section of tapered rectangular tube where all four walls are sloped about 10 degrees and the small end of the tapered tube fits your cooler exit, and the other end of the tube is bigger because of the slope of the walls. There is nothing really magic about 10 degrees. For very long diffusers, something like 2.5 degrees is the limit. For very short diffusers, up to 30 or 40 degrees can work, but generally have a lot of pressure loss. 10 degrees is a moderate diffusion angle for a short diffuser that should give you good pressure recovery.


I don't know the exit area of your cooler, but just as an illustration, if the cooler exit is 4" x 6" (24 sq in.) then a 3" long 10-degree diffuser would have an exit of 35 sq in. almost 50% increase in exit area compared to the cooler exit. That means that, assuming no diffuser pressure loss, the velocity through the cooler would be roughly 50% faster. Of course there are diffuser losses, so the velocity doesn't increase quite that much.
 
I don't think you gain much from any kind of splitter that shields the flow into the cooler from the flow into the cylinders. That flow has not picked up very much heat yet.

It does pick up some. Data from five years ago, taken during a trip to Jackson MS. Temp probe located at the face of the remote cooler, as compared to OAT under the wing. They were very close in the hangar. The OC air was taken from the rear baffle wall with a 4" SCEET:

Morning OAT 64F @ 8500 ft
Oil cooler inlet probe 81F
81-64= 17 degree rise

Afternoon OAT 86F @ 2500 ft
Oil cooler inlet probe 101F
101-86= 16 degree rise
 
It does pick up some. Data from five years ago, taken during a trip to Jackson MS. Temp probe located at the face of the remote cooler, as compared to OAT under the wing. They were very close in the hangar. The OC air was taken from the rear baffle wall with a 4" SCEET:

Morning OAT 64F @ 8500 ft
Oil cooler inlet probe 81F
81-64= 17 degree rise

Afternoon OAT 86F @ 2500 ft
Oil cooler inlet probe 101F
101-86= 16 degree rise

Thanks for sharing that Dan. The question is Will a splitter make any difference though? If the heat is radiating up from the #4 head, I would think I get a benefit. If it is picking up heat along the whole path from the cowl entrance, it doesn't help me, unless it is a long splitter going well forward. I had considered fabbiing a tubular structure take air directly from the entrance to the cooler. I found a guy that put the cooler where the filter is on hoizon induction and saw a significant improvement.

I read something interesting last night. Someone indicated that the portion of the head sitting right below the oil cooler entrance is the exhaust port chamber area and therefore much hotter than the rest of the head. This gave me pause to think. While I am sure it is hotter, it can't be 1000 or something like that or the aluminum structure would be compromised. Am I think that through correctly?

Larry
 
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Thanks for sharing that Dan. The question is Will a splitter make any difference though? If the heat is radiating up from the #4 head, I would think I get a benefit. If it is picking up heat along the whole path from the cowl entrance, it doesn't help me, unless it is a long splitter going well forward. I had considered fabbiing a tubular structure take air directly from the entrance to the cooler.

It's picked along the entire path. I did fly the system a few years with partially insulated ducting from the cowl inlets, and it lowered oil temperature. How much? I'd call it 8 or 10 degrees off the top. No surprise.

However, I think we're running off the rails. The question is why your previously acceptable temperatures changed. If none of the physical changes you made can be found responsible, it may be time to think about an increase in blow-by.
 
It's picked along the entire path. I did fly the system a few years with partially insulated ducting from the cowl inlets, and it lowered oil temperature. How much? I'd call it 8 or 10 degrees off the top. No surprise.

However, I think we're running off the rails. The question is why your previously acceptable temperatures changed. If none of the physical changes you made can be found responsible, it may be time to think about an increase in blow-by.

Unfortunately, I can no longer be sure the temps I am recalling from last fall are reliable. The hot weather was early in my phase I and I probably wasn't paying close attention to my oil temps as I was battling fuel distribution problems and cylinder glazing. Whenever I looked it was under 200. However, I found a couple of logs showing temps in the 215 range with ambient surface at 80*+. I unfortunately set my alarm level too high (230) and never got warnings. My initial problems this spring I am attributing to a partially blocked cooler that I replaced. With the plunger and new cooler I am getting a max of 210-215 and I have to assume that is what I was regularly getting last fall. I believe the high temps with the new cooler were due to V/T#2 being bad, as I can't replicate them with V/T #1 or the plunger.

I simply can't trust my observations and need to assume what I am getting now is similar to what I was getting then. I have an air oil separator, so hard to tell if I am getting an increase in blow-by. I have not noticed any measurable build up on the belly, so it is not enough to be over-running the separator. That said, I have read a few accounts of people running the same or smaller cooler with good results (190) on an O-320.

Larry
 
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If the blowby is a cause of high oil temps it will leave a tell-tale sign of rapidly-darkening oil. The oil will turn darker than usual, almost a shade of black as opposed to the usual olive-green tint.

Vic
 
Thanks for sharing that Dan. The question is Will a splitter make any difference though? If the heat is radiating up from the #4 head, I would think I get a benefit. If it is picking up heat along the whole path from the cowl entrance, it doesn't help me, unless it is a long splitter going well forward...

I think you are looking in the wrong direction for the benefit of a "splitter". While there is no doubt that the air at the rear of the upper plenum picks up some heat, consider that this is exactly where Rockets pull their cabin air vent from. In flight, the vent air is plenty cool for human comfort.

That said, I think there is plenty of benefit to providing a full height baffle against the fins of #4 rather than just leaving a hole for the cooler. The primary benefit is forcing the air through the fins of the head in an organized manner instead of the more meandering path around the fins/through the cooler. In such installations I typically see my #4/6 CHT drop noticably. The second possible benefit (unverified) is the blockage of radiant heat off the head that an aluminum baffle provides. Probably a minor effect, but it still counts in my book as a win/win. This does require a deviation from plans and you need to provide a bit of an air gap off the back of the cylinder, but for those building its usefull info.
 
Get some data.

I think you are looking in the wrong direction for the benefit of a "splitter". While there is no doubt that the air at the rear of the upper plenum picks up some heat, consider that this is exactly where Rockets pull their cabin air vent from. In flight, the vent air is plenty cool for human comfort.

That said, I think there is plenty of benefit to providing a full height baffle against the fins of #4 rather than just leaving a hole for the cooler. The primary benefit is forcing the air through the fins of the head in an organized manner instead of the more meandering path around the fins/through the cooler. In such installations I typically see my #4/6 CHT drop noticably. The second possible benefit (unverified) is the blockage of radiant heat off the head that an aluminum baffle provides. Probably a minor effect, but it still counts in my book as a win/win. This does require a deviation from plans and you need to provide a bit of an air gap off the back of the cylinder, but for those building its usefull info.

What is the air temp in and out of the cooler, and what is the oil temp in and out of the cooler? This is a good place to start. With the spec sheet it should give a good idea of what is going on. $120 will get a good thermocouple meter and some TC's from Omega. Money well spent for diagnosing a number of installation issues. Sell it later when all is well. Guessing will cost much more $, not to mention time. A cheap manometer and piccolo tubes will further quantify airflow issues, if they exist. These tools, IMO, are essential when when not building exactly to Vans plans, with Vans parts. Lets have fun with data!
 
Michael said: (above):

" is the blockage of radiant heat off the head that an aluminum baffle provides. "

I'm not addressing your situation or conclusions (haven't studied in sufficient detail to make an honest reasoned comment) but, lest others be led astray . .

Air doesn't pick up heat from radiation, rather from conduction.

FWIW
 
If the blowby is a cause of high oil temps it will leave a tell-tale sign of rapidly-darkening oil. The oil will turn darker than usual, almost a shade of black as opposed to the usual olive-green tint.

Vic

I have about 20 hours on my oil and it is light to medium brown. I could see it referred to as olive green. I had major blowby when I glazed my #2 early in Phase I and the oil was dark black after 10 hours, including visible chunks of carbon. Previous oil change was at ~40 hours and the oil was a medium - dark brown, but not black. The oil analysis was good, but I don't remember if that included a carbon analysis.

Does this seem normal?

Larry
 
Michael said: (above):

" is the blockage of radiant heat off the head that an aluminum baffle provides. "

I'm not addressing your situation or conclusions (haven't studied in sufficient detail to make an honest reasoned comment) but, lest others be led astray . .

Air doesn't pick up heat from radiation, rather from conduction.

FWIW

I think toolbuilder was referring to radiation from the heads to the cooler face - per the view factor, not preheated secondary air. He seems pretty savvy about these things. I would also think it to be small/irrelevant.

I did put a short wrap over the end of the head fins to prevent flow through to the cooler. Don't know if it works yet.
 
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