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Replace Vernatherm or install bypass plunger?

B

badmrb

Active Member
This summer my oil temps have been slowing creeping up. I pulled the vernatherm and boiled it. It is stretching .12 in. so from what Ive read its not functioning correctly and not seating any longer.

Ive also come across a couple folks mentioning the bypass plunger and manual controlled ball valve on the oil cooler. I really like the idea of being able to control oil temp and not have to remove cowl to add/remove foil tape from the oil cooler when the seasons change.

Ive found the plunger parts from Aircraft-specialties for about $45 shipped. I'd just need to source a ball valve and cable and fab mount. Seems like for half the cost of a replacement vernatherm I can solve problem as well as control temps without having to add a oil cooler air restrictor.

I quess what Im asking for is from someones that done this do they have any pictures of install and how they hooked up the cable for controlling the ball valve. Just some final guidance/pitfalls to look for.

Also, recommendations for a small/inexpensive vernier type cable to control the valve.

thanks
Steve
 
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badmrb said:
This summer my oil temps have been slowing creeping up. I pulled the vernatherm and boiled it. It is stretching .12 in. so from what Ive read its not functioning correctly and not seating any longer.
Click to expand...

Quick confirmation; per the Rostra Vernatherm factory drawing, extension is to be 0.160" between 150F and 185F. Valve tip is to close against seat between 183F and 187F. Cracking pressure is to be 60-90 psi with oil temp at 195F.
 
Steve,
I installed the plunger and chucked my vernatherm a couple years ago. My oil temp dropped by 10-15 degrees. I haven't installed the ball valve yet, but I'm planning on it. I have one - from HD or Lowes, and I haven't figured out rigging yet, but planning on a vernier control cable. Right now I'm using the Venetian blind thing from Vans in the winter only.

If you want excellent advise, call Larry Veterman. He uses this ball valve system and has great results with precise temperature control. I'm going to follow his advise and try the same thing. Good luck
 
Thanks Scott

I read some references to vetterman doing this but was figuring someone here had done this and taken pictures.

Im curious what this does to my oil temperatures. Before this summer i usually saw numbers in the 180's. Cant remember ever seeing over 200, even after long climb. When i started having to really pull power to just keep 210 i figured time to investigate.

I will probably get a couple new hoses made since these are very hard and at least ten years old. It will also let me decide exactly where to install valve. Just thinking someone has done this and figured out the "ideal" location.
 
Scott,

The reason you won't find much information or images on this modification is the vernatherm oil control system is fairly bullet proof, it is not generally messed with and there are legal issues in advertising such a change.

The Lycoming engine oil cooling system has been around a long time and generally works very well. When the engine warms up, the plunger closes the port to the engine and all oil is forced to the cooler. The up side is the cooler port is never closed - the down side is oil can be running through the cooler when it is cold outside.

What you propose to do is not bullet proof. A manually controlled plunger will require a device that is not proven and could fail with a major oil leak. The ball valve to the cooler is less a risk, they have been around a while but a plunger to the engine port will require an external hook up, pass through a sleeve of sorts and be able to withstand normal oil pressure. One would be reinventing the wheel for sure. (or perhaps you propose to permanently close the engine port internally, I don't know what you have in mind)

Larry Vetterman is (or maybe was) running with some type of control over flow to the cooler but as you have discovered, he has not made a big public deal over it and probably won't. I know there was a ball valve controlling oil flow to the cooler but it is unknown what the situation is with the plunger. To go with just the ball valve would fix the winter ops problem.

If the vernatherm is removed, that leaves both ports open all the time. It would not cure the summer operation where it is desirable to move all oil to the cooler, the engine port would be wide open.

I would investigate the cause of the rising oil temperature. It could be the vernatherm or something else. Perhaps the cooler is in need of service or the CHT's are running hotter. Oil cooling is very dependent on cylinder temperature, if CHT's go up, so will oil temperature. Also, the planet is warming up. Oil temperature will follow OAT if the cooling system is at its limit.

What engine do you have and what oil cooler supports it?
 
The plunger discussed is a stock Lyc part, spring loaded, no external control. With a ball valve in the cooler line.closed, oil pressure compresses the spring and the plunger retracts, unblocking the bypass port. Ball valve open, all oil flows through.cooler as the bypass remains blocked. Only risk is operator error.
 
DanH said:
The plunger discussed is a stock Lyc part, spring loaded, no external control. With a ball valve in the cooler line.closed, oil pressure compresses the spring and the plunger retracts, unblocking the bypass port. Ball valve open, all oil flows through.cooler as the bypass remains blocked. Only risk is operator error.
Click to expand...

Well, you learn something new everyday.

On what engines is it used rather than the the oil cooler bypass valve? (so called vernatherm)

The oil cooler bypass valve leaves the engine port open until the spring expands to close it.

The device you refer to holds the plunger in the bypass closed position until pressure overcomes the spring and then it opens, is that correct?

What happens if it does not open?
 
Actually, I am wanting to make a "bullet proof" setup. At least one that wont strand me somewhere like this failed vernatherm nearly did. I got to say that nearly $300 for a thermostat is crazy. As far as "the world getting warmer" . . . I'll leave that for other forums that specialize in the drinking of special refreshments.

I had been thinking the oil temp was higher than last year with it running in the 190's with me just putting around local at 2200rpm. Did a trip down to OK a few weeks ago and after climbing had to pull power way back in order to get temp back down close to 200. Definetly not the way I like to do cross country's. Then this last weekend I did a local flight for troubleshooting and I had power back to 1900rpm just to maintain 210.

Installing the by-pass plunger means oil is always going through cooler.. . . 100% Spring is just a pressure relief if cooler plugs. . .same principal as on the vernatherm. Valve setup would just be to limit that down during winter ops in order to control temp.

Until someone suggests a better setup, Ill probably be installing Plunger as soon as it arrives. Then if temps do what I want I'll add the Valve before winter. Just something simple. Adel clamps, cable end hooked up to valve handle with a cable capturing bolt ..mounted so as to give full travel.
 
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Steve,

Calling Larry Vetterman to talk about this is definitely a good idea, he is both knowledgeable and very helpful; you can't help but learn something!

There are certainly some risks involved, most notably the potential to forget to open the valve which could easily result in exceeding redline temperature. I would not recommend this setup unless you want to continuously monitor oil temperature. It adds flexibility, but also operational complexity. Adding a valve in the oil line also means there is one more set of connections that could possibly fail, or the control and its connections could fail.

I believe the plunger and spring were standard equipment in many engines that didn't come with a vernatherm (maybe someone else knows more about this history?). I think it is incorrect to say that the plunger always stays closed unless the oil cooler plugs. My understanding is that it also opens when the oil is cold, due to the higher pressures that build in cold, more viscous oil. See more discussion here for example:

http://www.avweb.com/news/maint/182617-1.html?redirected=1
 
David-aviator said:
The oil cooler bypass valve (ed: vernatherm) leaves the engine port open until the spring (actually a little capsule) expands to close it. The device (what Lyc calls a "viscosity valve")you refer to holds the plunger in the bypass closed position until pressure overcomes the spring and then it opens, is that correct?
Click to expand...

Correct. Be aware the spring on the vernatherm serves the same pressure release function when the vernatherm has extended to close the bypass.

What happens if it does not open?
Click to expand...

All oil flows through the cooler. If viscosity is high, pressure in the cooler may be high. High enough to pop it? I dunno. That would depend on a lot of other factors.

Alan Carroll said:
There are certainly some risks involved, most notably the potential to forget to open the valve which could easily result in exceeding redline temperature. I would not recommend this setup unless you want to continuously monitor oil temperature.
Click to expand...

Entirely agree, although operationally it may not be real difficult. The manual cooler valve would be open for every takeoff and almost all the time in hot weather. You would close it mostly for cold weather cruise. Operation could be intuitive if the valve control was rigged in the same group as the throttle/prop/mixture, with the same convention for motion...all forward (open) for max power.

See more discussion here for example:

http://www.avweb.com/news/maint/182617-1.html?redirected=1
Click to expand...

Good article, but there is one dumb statement worth noting, in the interest of reducing confusion:

On the other hand, if the gauge is showing a comfortable margin from red line and the actual oil temperature (ed: measured through the dipstick tube) is 200 degrees, not only do you need a new gauge, but you've probably got some other problem, too.

The sump temperature is always hotter than the indicated oil temperature. Sump oil just returned from visiting the hot parts. The oil temperature sensor is in the flow just downstream of the oil cooler. It indicates inlet temperature.
 
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I have one installed and I like it

I finally decided to remove my Vernatherm and install the spring/plunger and ball valve.

My particular problem was that I could not get my oil temps up sufficiently in the winter. I tried blocking the front of the cooler, the rear of the cooler and had Vans adjustable air control to install and started researching the ball valve. (They seemed equal complexity and if I did not like the ball valve, I could always install the shutter using the same push-pull).

I installed a push-pull from ACS http://www.aircraftspruce.com/catalog/appages/a700.php

This is the ball valve from McMaster Carr 4465K21 - installed on the oil cooler inlet.

IO-360, Vans standard oil cooler on plenum behind #4 per Vans instructions.

After installing the ball valve - I could set my oil temperature to 180 in Minnesota winters.

In Minnesota Summers, 90 something degrees with the ball valve open, I see oil temps in the 150's.

Yes it is one more thing to have to set.

Made it part of the checklist - no worse than mixture - RICH

I have Dual GRT's, VP200 and an EIS 4000 all set to alarm if the oil temp goes above 190.

Bottom line - for me, works like a champ.

Usual disclaimers, blah-blah-blah.

I did take some photos which I don't have at the office. If you PM me, I will send them to you.

Best
 
David,
As Dan says the plunger (stock Lycoming part) is actually called a viscosity valve and is not manually controlled. On my RV8 I have a 90 degree oil filter adapter and spacer - necessary to clear the engine mount. This spacer sits on the accessory case very loosely (the bolt holes are larger than those in the adapter and case. The vernatherm, which is installed in the oil filter adapter, seats on a hole in the face of this ill fitting spacer. It's nearly impossible to get things lined up in such a way that the vernatherm face seats completely in the hole - allowing some of the hot oil to continue to bypass the cooler. I tried to adjust this to get it to seat all the way around the circumference, but was unable to. Removing the vernatherm allowed all hot oil to go through my cooler and made a noticeable difference.

Larry Veterman was very helpful and encouraging about the use of a manually controlled bypass valve to be used in the cold months. He stressed the importance of making sure that even in the full bypass setting of the control (knob all the wat out), the ball valve is not to be fully closed, allowing some oil through the cooler. He gets superior results with this setup.

There is the possibility of forgetting to open the controll all the way (knob fully in) on takeoff. There is also an equal likelihood of taking off with the carb heat on, a mag off, the canopy not latched, mixture not rich, control locks not removed, dog leash still tied to your tail wheel, etc......

If oil temp is an issue, I think this process is worth considering, fully taking into account operating requirements and procedures.
 
Scott, I sent you a PM with my email for your pictures. I really appreciate it. Just what I was looking for.

Also, Scott Hersha, good point on setting the cable travel so as not to completely close the cooler off.


I know its something else for the checklist but certainly not any more complicated or more likely to forget than the air controls for the oil coolers are, cowl flaps, etc... Probably will be one basic setting for summer ops and another for winter with the ability to fine tune for different power settings.

I know a few years ago we had a warm spell early in the year and I had oil temps too high because I was still running the cooler taped. Red light from EIS went off warning me of oil temp. Off course landed, removed cowling, removed tape, and went flying again. Then spent the next month or better running way too cool oil temps until winter really was over.
 
badmrb said:
I know its something else for the checklist but certainly not any more complicated or more likely to forget than the air controls for the oil coolers are, cowl flaps, etc... Probably will be one basic setting for summer ops and another for winter with the ability to fine tune for different power settings.
Click to expand...

If you have an electronic engine monitor I'd also suggest setting an oil temperature alarm to go off at some point below redline (say 225?), as a nag to open the valve. I'll bet a beer you'll see the alarm go off at some point! Its easy enough to remember when you're doing a normal takeoff checklist etc., but its a bit easier to forget when initiating a climb, doing maneuvers or slow flight, chugging along at 90 knots enroute to Fisk, or during a long taxi.

That said, it is very nice to be able to control your oil temperature within a degree or two.
 
Scott Hersha said:
David,
As Dan says the plunger (stock Lycoming part) is actually called a viscosity valve and is not manually controlled. On my RV8 I have a 90 degree oil filter adapter and spacer - necessary to clear the engine mount. This spacer sits on the accessory case very loosely (the bolt holes are larger than those in the adapter and case. The vernatherm, which is installed in the oil filter adapter, seats on a hole in the face of this ill fitting spacer. It's nearly impossible to get things lined up in such a way that the vernatherm face seats completely in the hole - allowing some of the hot oil to continue to bypass the cooler. I tried to adjust this to get it to seat all the way around the circumference, but was unable to. Removing the vernatherm allowed all hot oil to go through my cooler and made a noticeable difference.

Larry Veterman was very helpful and encouraging about the use of a manually controlled bypass valve to be used in the cold months. He stressed the importance of making sure that even in the full bypass setting of the control (knob all the wat out), the ball valve is not to be fully closed, allowing some oil through the cooler. He gets superior results with this setup.

There is the possibility of forgetting to open the controll all the way (knob fully in) on takeoff. There is also an equal likelihood of taking off with the carb heat on, a mag off, the canopy not latched, mixture not rich, control locks not removed, dog leash still tied to your tail wheel, etc......

If oil temp is an issue, I think this process is worth considering, fully taking into account operating requirements and procedures.
Click to expand...

Scott,
Thanks for the good information on this subject.
It is understandable why guys are going that route, some RV do need it summer and winter.
 
I was able to install plunger and spring last night after work. I also removed the vernatherm end and just put the housing back in.

Didnt get much of a flight in before running out of sunlight but here are some initial observations.

Took off and climbed a couple thousand feet. Leveled off and set "sight seeing cruise setting" of about 2150 rpm and 130kts. Temp rose very slowly and finally settled at 170. A nice drop from the 210 of the last flight. Outside temps were very similar at about 78 degrees, just different altitudes.

Decided to add some power on the way back. Ran into the yellow at 160+kts, about 2450 to 2500rpm. . Oil temp actually stayed at 170 or dropped a degree or two. Got back to the airport, started easing power back and doing a few tight circles to bleed airspeed and descend. I did notice temp crept up to 180 in the pattern with about 70kts airspeed.

So, high oil temp solved. Now I probably have a month or so before temperatures drop enough that too cool becomes the norm. :) I just need to install a ball valve and control cable to take care of that.

My hoses have the reuseable end fittings, so I just need to get the fitting tool, a couple more fittings, ball valve, and new length of hose.

If anyone has pics of how/where they installed the valve and cable I would really appreciate it.

thanks
Steve
 
What is considered HIGH OIL TEMP by Lycoming ????

:confused: I have been following this thread and am a bit confused ? I have always been told that to get rid of the water in the engine , I should run my engine for at least 1/2 hr. at 212 deg. (water boils at this temp,) , and that Max Oil temp is 240 deg. plus ?? not really defined by the factory . If this is TRUE , then why does everyone want to run at 180 to 190 deg. ?????? What's wrong with a crusing temp of , let's say 220 deg. ??? ALL DAY LONG !
 
HIIFLY said:
:confused: I have been following this thread and am a bit confused ? I have always been told that to get rid of the water in the engine , I should run my engine for at least 1/2 hr. at 212 deg. (water boils at this temp,) , and that Max Oil temp is 240 deg. plus ?? not really defined by the factory . If this is TRUE , then why does everyone want to run at 180 to 190 deg. ?????? What's wrong with a crusing temp of , let's say 220 deg. ??? ALL DAY LONG !
Click to expand...

Foremost, understand that we're discussing INLET temperature, measured just after passing through the oil cooler. It is lower than sump temperature, and far lower than the temperature of the small oil quantity circulating through the cylinder heads.

I'd guess sump temp is typically 15F warmer than inlet temp. It may be more. For sure some of the oil circulating in the engine gets a lot warmer before it rejoins the sump quantity.

Take a look at the Lycoming operating manual for your engine. One of the latest to be published is for my IO-390. It is quite clear:

(f) Oil Temperature: The maximum permissible oil temperature is 235F (113C). For maximum engine life desired oil temperature is 180F (82C).

Last, there is no need to achieve 212F to remove water. Water evaporates perfectly well at lower temperatures. Need convincing? Put a water pot on the stove, raise the water temp to 180F, and see how long it takes for the pot to go dry.
 
Oil Temps

Thanks Dan for your response , and I did look at my eng spec. info. . What it says is "at average ambient temp of 30deg F. to 90 deg F. , engine operating temp. DESIRED = 180 deg F. to Max 245 deg F. Oil Temp ." My Question is what is wrong with cruising temps in the middle ??? Why does everyone strive for the low end ??
A friend of mine who has a Pitts S2B 260 HP LYC . asked a Lycoming Tec. at Oshkosh one year not long ago about his Cyl. head temps. being at cruise around 420 deg . , and the Tec. asked my friend what was MAX Temp listed in the manuel for the Cly's . My friend said to the Tec . 500 deg., The Tec said to my friend , SO WHAT'S YOUR PROBLEM ????
 
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