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More vernatherm questions

Christopher Murphy

Well Known Member
Im having an issue with my o-320 in my RV4. I never had higher than 210 deg oil temps on the hottest 100 plus degree days. Then one day (85f) it ran up to about 220 and I started looking for the reason. I have checked all the baffles and the cht are all 350 or less. I checked for obstruction in the oil cooler scat tube. I pulled the vernatherm and checked it in a pan of hot water and it was not extending the correct distance by about .030 inch so I replaced it. I still have the high oil temp issue so I replaced the cooler. No help.

Any suggestions from you engine gurus? I replaced a broken temp sensor before all this started and tested the sensor and guage with boiling water test and it appeared to be accurate.

How sensitive is the seat of the vernatherm? I know the seat can be reworked for a better seal. Is that fairly common? The engine has 1150 hours on it

Is there a way to check to see if oil is flowing through the cooler? Thermal scan?
This has me stumped.

Thanks in advance.
 
Cooler

Not likely your issue. How is oil pressure, low pressure can cause higher temps. 220f is upper limits, but not a point where you’ll have a failure. How much oil do you run/qts, what viscosity ? Do things cool off with outside temps going down?
 
Hi oil temp

I run the same oil as ever. 15w50 in winter then usually run 100w 50weight in summer but i have run 15w50 in summer too. 7 quarts always add at 6 qts.
I did tweak oil press up from 65 to 75 a while back. No difference in temps
This just started on long cross country flight. Was running about 200 on a hot day then it went up to 220 and i cant get it back down. Im talking the a shop about re cutting the vernatherm valve seat but the old vernatherm looks like it was well seated. Im going to pull the new one out and see what it looks like.

The engine shop has a thermal scanner and im hoping to compare temps at the sender or filter to temps at the oil cooler.

Got me stumped this engine has always run on the cooler side
Cm
 
I’ve had a partly clogged oil cooler, but that was a very old one, around 30 years of age... similar symptoms, the vernatherm also tested ok. Maybe?
 
Are you starting to notice your oil getting dirty sooner than it used to? I had an angle valve that just like flipping a switch the oil temp jumped 20degrees. I did everything you did plus some. Nothing helped.
Mahlon opined in bringing up the oil color. He surmised that possibly getting just enough blowby of the rings that the hot oil just finally overcame the cooling capability of the system. I went to a 4 inch duct into a 14 row cooler and that finally got it back under control.
Just a thought. Kind of like an air conditioner can keep a house cool until it gets over a 100 outside. It’s pumping it’s little heart out but once it get’s behind the curve, it won’t keep up.
 
I think that if you want to eliminate the vernatherm operation and/or seat condition as a variable, the easy thing to do is drop in a viscosity valve and spring and go fly. If you have the factory oil filter housing and the viscosity valve does not share space with the vernatherm, this is a 10 minute installation once the cowl is off. My guess is that you will get an immediate and dramatic reduction in oil temp. If not, you have a legitimate oil cooling issue.
 
Your original vernatherm probably failed and the replacement did not expand to the correct length. I have an mechanic buddy who was chasing high oil temp for weeks in a TR1. He determined that vernatherm was too short and called a parts shop and ordered a new one. The parts guys suggested he buy three, heat them in boiling water, measure each and keep the longest one and send the other two back. He installed the longest one and solved his problem. Just one data point that might worth exploring. Dan from Reno
 
No. It runs very clean

Are you starting to notice your oil getting dirty sooner than it used to? I had an angle valve that just like flipping a switch the oil temp jumped 20degrees. I did everything you did plus some. Nothing helped.
Mahlon opined in bringing up the oil color. He surmised that possibly getting just enough blowby of the rings that the hot oil just finally overcame the cooling capability of the system. I went to a 4 inch duct into a 14 row cooler and that finally got it back under control.
Just a thought. Kind of like an air conditioner can keep a house cool until it gets over a 100 outside. It’s pumping it’s little heart out but once it get’s behind the curve, it won’t keep up.

No this engine runs very clean no signs of blow by at all.
Cm
 
I think that if you want to eliminate the vernatherm operation and/or seat condition as a variable, the easy thing to do is drop in a viscosity valve and spring and go fly. If you have the factory oil filter housing and the viscosity valve does not share space with the vernatherm, this is a 10 minute installation once the cowl is off. My guess is that you will get an immediate and dramatic reduction in oil temp. If not, you have a legitimate oil cooling issue.

Please elaborate on this viscosity valve.
Where to get one, how to install it.
I really want to see if its a problem with the vernatherm or seat
Cm
 
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Check he flared seat that the vernatherm nose seals against. These can become deformed and there is an SB on how to reform it. If the nose doesn’t seal, not all f the oil goes to the cooler

Larry
 
Type 1?

..........


Thanks Dan, I assume a Type 1 vernatherm operates on viscosity vs. temperature
Expansion. Ive read about its use on earlier engines.

If it costs as much as my replacement vernatherm or is no longer available, this method of troubleshooting is academic.

I will ask the engine overhaul shop Ive been consulting with if they have one to borrow.

Cm
 
Ive read the SB and

Check he flared seat that the vernatherm nose seals against. These can become deformed and there is an SB on how to reform it. If the nose doesn’t seal, not all f the oil goes to the cooler

Larry

The old vernatherm was not extending all the way. However the witness marks on it showed that It was contacting the seat 100 percent at least at some point. Looking at the seat visually didnt appear to be damaged. Its hard to believe a tiny gap there could make a 20 or 30 degree difference in temps

Im going to pull the new one out and re check it. The engine shop tells me machining the valve seat is no longer a satisfactory repair and lyc. Recommends a whole new filter adapter.
Thanks for your input here.
Cm
 
Thanks Dan, I assume a Type 1 vernatherm operates on viscosity vs. temperature
Expansion. Ive read about its use on earlier engines.

Not a vernatherm, just a spring and piston. Yeah, pretty common, like VW air cooled flat 4's. When the oil is cold and thick, viscosity makes it hard to push through the cooler, so it compresses the spring instead, raising the piston enough to unport a bypass.

If it costs as much as my replacement vernatherm or is no longer available, this method of troubleshooting is academic.

Dirt cheap when priced in AMU's ;)

Mike referenced some Spruce prices earlier.
 
Not a vernatherm, just a spring and piston. Yeah, pretty common, like VW air cooled flat 4's. When the oil is cold and thick, viscosity makes it hard to push through the cooler, so it compresses the spring instead, raising the piston enough to unport a bypass.

...Dirt cheap when priced in AMU's ;)

Mike referenced some Spruce prices earlier.


Indeed. I could not find a used plunger from any of my junk sources so popped for brand new from Spruce. But the spring.... No way was I going to spend $40 bucks on a 50 cent spring... That one I DID find a functional replacement in my stash.

All told, under $30 bucks and 15 minutes install time was some of the least expensive and most effective troubleshooting I have done on this airplane.
 
Oil pressure maybe?

..........

My last thought about this is…

Ive had to tweak my oil pressure up a couple times in the last 100 hours or so. Im wondering if my oil press guage is failing and giving a false low reading and as I tweaked the press up, Is it possible i have caused the vernatherm valve to unseat due to higher oil pressure? Anyone know at what pressure that would happen. In anycase new press and temp guages and sensors are ordered

Cm
 
Update on vernatherm.

Please see post #6. Plunger is about $25 from Spruce; spring is insane ($40). I have the dimensions of the Lycoming spring if you want to shop at the local hardware store for one.

https://vansairforce.net/community/showthread.php?t=189458&highlight=Viscosity+ball+valve

I finally pulled the oil filter adapter off and had the shop dress the valve seat. I tested the newer vernatherm and it expanded a total of .200 in. Reinstalled the vernatherm using the thinner continental type gasket. Test flight did not show a
Real decrease in temps.

The gage is acurate to the degree. As I had replaced the oil temp probe about the same time this all started im going back to it.

The replacement probe is shorter and barely protrudes out of the bushing as installed on the filter adapter. Im wondering if this could cause a 15 or 20 degree increase on the gage.?

Grasping at straws.
Cm
 
You might want to check your ignition timing. A few degrees advanced will push the oil temp up quick. If your engine is creating a lot of heat the vernaterm will just close and sit there, that's all it can do.
 
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You might want to check your ignition timing. A few degrees advanced will push the oil temp up quick. If your engine is creating a lot of heat the vernaterm will just close and sit there, that's all it can do.

Thanks but
The mags are timed pefectly. The compressions are good , no blow by or cylinder issues, the cht are good unchanged,
The cooler is good,the oil press is good, the baffles are good. Ive tested the gage and the probe. Im stumped.
Cm
 
I finally pulled the oil filter adapter off and had the shop dress the valve seat. I tested the newer vernatherm and it expanded a total of .200 in. Reinstalled the vernatherm using the thinner continental type gasket. Test flight did not show a
Real decrease in temps.

The gage is acurate to the degree. As I had replaced the oil temp probe about the same time this all started im going back to it.

The replacement probe is shorter and barely protrudes out of the bushing as installed on the filter adapter. Im wondering if this could cause a 15 or 20 degree increase on the gage.?

Grasping at straws.
Cm

Throw a viscosity valve in there and see what happens. Just leave the vernatherm installed.

Since my change, I cant get the oil warm enough. I used to cruise at 220, now I have a hard time getting above 175.
 
The gage is accurate to the degree. As I had replaced the oil temp probe about the same time this all started im going back to it.

The replacement probe is shorter and barely protrudes out of the bushing as installed on the filter adapter. I'm wondering if this could cause a 15 or 20 degree increase on the gage?

I've wondered too, but never made the effort to test. My own short sender probe appears to indicate 7~9 F warmer than reality. The way a standard AC style adapter is arranged, there may be some stratified flow along the top of the passage to the filter. Or perhaps the upper part of the adapter is simply warmer than the lower; given any flow at all through the vernatherm port, the upper is full of hot oil, direct from the engine. In past discussions here, we talked about installing another probe downstream of the filter, where all flows would be well mixed.

Yeah, it's spitballing, but if you have a longer sensor handy...
 

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I think I have one or two of those plungers in my hangar. I will check tomorrow and let you know.
 
Thanks for the input

I think I have one or two of those plungers in my hangar. I will check tomorrow and let you know.
Axel
Im not sure there is a place to put that plunger on my engine. Im going to keep trying to figure this out.

Ive been through all of lycomings trouble shooting
Documents.

Cm
 
Christopher,

Re the plunger location, see the illustrations below. Goes under a cap at the top of the main oil passage from the pump.

BTW, sometimes you'll see a builder website with the oil temperature sender installed in that hole, rather than in the correct location on top of the filter adapter. It won't read oil temperature correctly if installed there. No real flow past the sender, and none from the oil cooler.
.
 

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I finally pulled the oil filter adapter off and had the shop dress the valve seat. I tested the newer vernatherm and it expanded a total of .200 in. Reinstalled the vernatherm using the thinner continental type gasket. Test flight did not show a
Real decrease in temps.

The gage is acurate to the degree. As I had replaced the oil temp probe about the same time this all started im going back to it.

The replacement probe is shorter and barely protrudes out of the bushing as installed on the filter adapter. Im wondering if this could cause a 15 or 20 degree increase on the gage.?

Grasping at straws.
Cm

If the vernatherm is performing within spec in it's testing and the seat has been dressed while maintaining appropriate clearances, I would be looking at the cooler for blockage. One flaw in the Lyc is that oil flows through the cooler BEFORE the oil filter. The passages in the cooler are small, allowing debris to build up, if present. May be worth a 100 bucks to send the cooler to one of the shops that do ultrasonic cleaning.

If you question the sender, you can install an inexpensive probe into the sump to get another reading. I would expect sump temps to be around 10-20* higher than the reading in the filter housing, but have never done measurements to confirm that.

Larry
 
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Oil cooler

Already replaced oil cooler. The one I took off was fine.
That was in the checking the obvious phase..checked hoses too. Made sure there was not a bubble of air in the cooler

Thanks.

Cm
 
Now that you have been provided pictures of the viscosity valve location, have you been able to determine if your engine has those provisions? If it does have those provisions, do you intend to stick a valve in there and try it?
 
Now that you have been provided pictures of the viscosity valve location, have you been able to determine if your engine has those provisions? If it does have those provisions, do you intend to stick a valve in there and try it?

I may try a viscosity valve since there is a provision for it on the accessory case. I will have to get one first.

I used a digital thermometer today to measure some temps in different locations today. What I saw makes me think im not getting an accurate measement at the sender.

Cm
 
Mixing oils

The W100 oil is recommended between 60-89 F outside air temp.
The W15-W50 is recommended for all outside air temperatures.
I have flown with a mix of both oils.
When outside temp was about 45-50 F I saw increased oil temp.
Looking for the cause i finally found the problem.
The thicker W100 did not flow fast enough through the oil cooler.
You can test this, fly with slower air speed, this will raise oil cooler temperature.
Or you can partly block the airflow to the oil cooler.
Running with only W15-W50 will fix the problem.
Please note that flying in cold weather < 40 F may cause oil temperature
of > 240F. I'm not saying that this is valid for all installations.
My engine is a Superior IO-360 parallell valve 180 hp with external oil filter.

Good luck
 
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