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Lycoming Accessory Case Oil Schematic

DanH

Legacy Member
Mentor
It is all too easy to be confused about the Lycoming vernatherm, oil filter, oil cooler, and accessory case oil flow, as the available Lycoming drawings are a bit sketchy. What we need around here is a good functional system schematic, so I sat down with a cup of coffee this AM and drew one.

No copyright. Feel free to save a copy or distribute as you please.

Lycoming%20Oil%20Schematic.jpg


FYI, here are photos of the standard Lycoming (AC) oil filter adapter. The parts are arranged differently on other adapters (like the right angle models), but the functions are all the same.

Lyc%20Oil%20Filter%20Adapter%201.jpg


Lyc%20Oil%20Filter%20Adapter%202.jpg


Lycoming schematic from the manual, entire engine:

Lycoming_oil_schematic.jpg


Carl from New Zealand posted excellent photos and a system description last year:

http://www.vansairforce.com/community/showpost.php?p=207691&postcount=1

Carl's photo, posted here in case it drops elsewhere:

Processed_Img_4660.jpg
 
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Dan,
Where exactly is the oil temperature sender located (in the schematic)?
(and oil pressure sender as long as you're at it).

Thanks,
Mike
 
Thanks!

Good job.

That's exactly what my friend Charlie was looking for.

Have some more coffee and maybe we'll get even more documentation (hahaha).

Barry
Tucson
 
Mike,
Drawing edited per your request.

Remember, although a schematic may mimic physical appearance, the schematic location of components is based on function.
 
Dan-
Great schematic. Any chance you could add flow direction indication on the lines?

Alex
 
Don't want to derail the original post, but I have a few questions about my oil filter adaptor (just got it yesterday). A 90 deg adaptor did not fit my RV-4 conical mount so I got this one from Superior Air Parts. I did not receive any documentation. Got a call into them but no joy yet.


Is this the proper orientation? In this pic is up, up?

CIMG3112.JPG


What goes in "A"? Temperature sensor?

CIMG3113a.JPG


What goes in "B"? Vernatherm? Do I remove mine from the engine and put it in "B"? If so, how do I plug the "hole" on the engine after I move it.

CIMG3114B.JPG


What is the oil flow doing in "C", "D", and "E"?
CIMG3115C.JPG


Thanks for any help.
 
Thats a great set of questions Axel. I have the very same adapter to put on my IO-540 and was wondering about the same issues. I too will be waiting for someone to come to the rescue!
 
Is this a test? <g>

(1) yes
(2) yes
(3) yes, and are you sure you already have a vernatherm in your engine?
(3) Adapter is upside down in the photo. C is oil in from the cooler. D is oil in direct from the pump. E is oil out to the 1-3 engine oil gallery. This adapter doesn't have a built in pressure relief valve to accomodate filter element clogging.
 
What's this hole for?

I made this post today in this section, but no luck in getting an answer.
http://www.vansairforce.com/community/showthread.php?t=45603

A very small hole (approx. 1/16" dia.) in the mounting surface that exits into the main cavity. There's a matching hole in the accessory case and the gasket also has same hole.

oiladapter.th.jpg
[/URL][/IMG]

The reason I ask is that I got a 3/4" extension for the adapter from ECi, but it does not have the small hole in it.

My engine is an ECi O-360

Sure would appreciate any help on this.
 
Ok Sam, you made me curious. Stick a wire into the matching 1/16" hole in the accessory case pad. Is it drilled through to a cavity, or is it merely a blind hole?
 
Is this a test? <g>

(3) yes, and are you sure you already have a vernatherm in your engine?


Yes this is a test. Can you please grade your own answers?

My engine has what this picture shows as "oil plunger". Is that a vernatherm?
Processed_Img_4660.jpg
 
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Ok Sam, you made me curious. Stick a wire into the matching 1/16" hole in the accessory case pad. Is it drilled through to a cavity, or is it merely a blind hole?

Dan,
Good question.
I'll check that when I get back to the airport later today. Stand by.

Sam
 
<<My engine has what this picture shows as "oil plunger". Is that a vernatherm?>>

No. Most likely it is just a plug, but it may have a spring and plunger installed under the plug. If so, remove the spring and plunger.

Lycoming%20Oil%20Cooler%20Bypass%20Plunger.jpg


The spring and plunger can best be described as an historical remnant. They date from the days before Lycoming's introduction of the vernatherm. Here is a page from Lycoming SI-1008B, circa 1966.

Lyc%20SI%201008B%20Vernatherm%20Install.jpg


In the pre-vernatherm days all oil went to the cooler, all the time. The spring and plunger served as a pressure relief bypass in the event oil cooler flow became blocked. The introduction of the vernatherm made the spring and plunger unnecessary; the vernatherm has both a thermostatic plunger and a pressure relief spring.

Important note: take a close look at the cutaway drawing in the upper right of the 1008B illustration. If you're using an old-fashioned oil screen (unlikely) or a filter adapter with the vernatherm oriented like the old oil screen (your right angle adapter), it is possible for the tip of the vernatherm to foul the oil plunger if you have both installed in the same engine. There's another Lycoming SI addressing this issue.
 
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No. Most likely it is just a plug, but it may have a spring and plunger installed under the plug. If so, remove the spring and plunger..

VAF never ceases to amaze me with the timeliness of threads (pun intended). Just yesterday evening I removed this plug from my engine. It was leaking oil so I replaced the crush washer underneath it. I had no idea what that thing was used for...until now!
 
Mystery hole

Ok Sam, you made me curious. Stick a wire into the matching 1/16" hole in the accessory case pad. Is it drilled through to a cavity, or is it merely a blind hole?

Dan,
First of all there is NOT a matching hole in the accessory case for the small hole in the adapter. I don't know what I was seeing...but any way, there's not one there.

However, I still would like to know what the small hole is in the filter adapter.
Here are a couple of pics. One showing a wire through to the cavity and one showing the gasket with a provision for the hole.

eb6hdz.jpg
[/IMG]


24faecz.jpg


Since it would be blocked-off by the accessory case or by the 3/4" extension that I plan to install, it would seem that it serves no purpose on my engine?? :confused:

Thanks,

Sam
 
<<it would seem that it serves no purpose on my engine??>>

Looks that way to me, but call ECI, ask, and report back.
 
the tech guy with ECi thought ...

<<it would seem that it serves no purpose on my engine??>>

Looks that way to me, but call ECI, ask, and report back.

...that it was going to be used as some way of emptying the oil filter of oil at change by allowing air through the orifice to break the vacuum lock. That was his thought anyway. He seemed to think that it was an idea that didn't develop and that it's not used anymore and gets blocked off by the accessory case (or extension if used).

If someone knows more about it than what I found out from ECi, then please let us know.

Build on.
 
<<used as some way of emptying the oil filter of oil at change by allowing air through the orifice to break the vacuum lock.>>

Empty the oil filter? Hmmm.

If the accessory case pad was drilled to match the mystery hole, I think it would open a passage to the gear cavity, which would be the same as going to the sump. If somebody has a loose accessory case perhaps they could check that.

Such a hole wouldn't introduce air for filter draining. However, if you punched an air hole in the end of the filter, the drilled hole would drain the filter contents to the sump.

Of course it would also be a constant pressure leak when the engine is running...and that may be why it is not used.
 
...that it was going to be used as some way of emptying the oil filter of oil at change by allowing air through the orifice to break the vacuum lock. That was his thought anyway. He seemed to think that it was an idea that didn't develop and that it's not used anymore and gets blocked off by the accessory case (or extension if used).

If someone knows more about it than what I found out from ECi, then please let us know.

Build on.

I've been doing a mod to a standard old oil screen body and wanted to revisit this thread to add some additional comments. I noticed the small hole in the screen body and gasket and wondered what it was for then it dawned on me and figured I'd answer the question here. I am not using a vernatherm in favor of using a ball valve to manually control temperatures and realized that without the vernatherm and with the oil cooler bypass plunger installed the screen body would remain pressurized at shutdown. Enough that without the small hole, someone pulling the screen housing off would get a nice splash of oil without it. So that is what the small hole is for.
 
oil filter adapter

Hi Dan. Looking at your original post and pics from 2009, I have an adapter tisactly like yours. I'm guessing that the red cap looking part is the cover for the opening that will hold the oil temperature sender that provides a signal to my gauge on the panel, yes? Also, after reading this thread and looking at the pics and schematics and I'm still not sure where the oil pressure swith goes that sends the signal to my Hobbs and low
OP light. Thanks for any information you might have about this.
 
I'm guessing that the red cap looking part is the cover for the opening that will hold the oil temperature sender that provides a signal to my gauge on the panel, yes?

Yes.

I'm still not sure where the oil pressure swith goes that sends the signal to my Hobbs and low OP light.

In general, best practice is to not mount mechanical switches and mechanical oil pressure senders on the engine itself. Most folks run a hose from the oil pressure port (near the upper right engine mount) to a remote-mounted sender.

Solid state devices do fine on the engine, a temperature sender being a good example.

Current glass EMS systems don't use a on-off switch to detect oil pressure for a hobbs or warning light. The user merely sets internal limits in the EMS. If you're a steam gauge guy, insert a tee for the switch into the pressure line going to the remote sender, or mount the switch on a manifold with the sender.
 
I've been doing a mod to a standard old oil screen body and wanted to revisit this thread to add some additional comments. I noticed the small hole in the screen body and gasket and wondered what it was for then it dawned on me and figured I'd answer the question here. I am not using a vernatherm in favor of using a ball valve to manually control temperatures and realized that without the vernatherm and with the oil cooler bypass plunger installed the screen body would remain pressurized at shutdown. Enough that without the small hole, someone pulling the screen housing off would get a nice splash of oil without it. So that is what the small hole is for.

Wow!....after all these years...
Thanks, Bob!
 
pressure switch

If you're a steam gauge guy, insert a tee for the switch into the pressure line going to the remote sender, or mount the switch on a manifold with the sender.

I am a steam gauge guy, for now. I have an extra line for my fuel pressure that Van's provided. Since I won't be using that part of the firewall mounted manifold, I will figure out a way for the oil pressure line going to the manifold/pressure/transducer to also provide the pressure to activate the switch. I was just hoping there was a port/fitting/spot/oraface that was designed into the accessory case for this pressure switch that I couldn't find.
Thanks again.
 
So that is what the small hole is for.

And now, direct from the Department of Esoteric Lycoming Knowledge...;)

It appears to be an oil supply passage to the camshaft idler gear (the one with the fuel pump cam lobe), on an O-235, or O-290, or maybe a few others.

O-235%20Accessory%20Case%20outside.JPG


O-235%20Accessory%20Case%20inside.JPG
 
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Dan,

I've been trying to track down a high oil temp (no other abnormal indications) on my O-320 for a while and your diagram has been a fantastic help in that end - thanks for making it!

A quick question - if the Vernatherm is removed and the pressure relief plunger and spring are re-installed, does that change the oil flow from Pump-Cooler-Filter to Pump-Filter-Cooler? I've been looking at pictures of accessory cases for a couple of days now trying to visualize the passageways and can't quite do it. My engine is still whole so I can't put hands on the inside of the accessory case to figure it out either.

Thanks!
 
A quick question - if the Vernatherm is removed and the pressure relief plunger and spring are re-installed, does that change the oil flow from Pump-Cooler-Filter to Pump-Filter-Cooler?

No. Flow path remains pump -> cooler -> filter...except when viscosity is high. When viscosity is high (think cold oil), resistance to flow through the cooler forces the plunger and spring upward, uncovering the bypass hole into the filter adapter, and thus partially bypassing the cooler.

How partial? Note as described above, the cooler's resistance to flow determines how far the "viscosity valve" (Lycoming's name for the plunger and spring) opens. That resistance varies between coolers. For example, a two-pass SW/Meggitt 8432 has a pressure drop of 15 psi or so at 4-cyl flow rates, while a similar single pass cooler (example 10599) is about 5 psi. For any given RPM, more oil bypasses the 8432.

Adding a ball valve in the cooler line allows forcing all flow to the bypass port. That results in fast warmup, but won't help a hot oil problem. When fighting "too hot", installing a viscosity valve and removing the vernatherm is mostly just a way to check the latter. If it cools well, the vernatherm was not extending to close the bypass.
 
No. Flow path remains pump -> cooler -> filter...except when viscosity is high. When viscosity is high (think cold oil), resistance to flow through the cooler forces the plunger and spring upward, uncovering the bypass hole into the filter adapter, and thus partially bypassing the cooler.

How partial? Note as described above, the cooler's resistance to flow determines how far the "viscosity valve" (Lycoming's name for the plunger and spring) opens. That resistance varies between coolers. For example, a two-pass SW/Meggitt 8432 has a pressure drop of 15 psi or so at 4-cyl flow rates, while a similar single pass cooler (example 10599) is about 5 psi. For any given RPM, more oil bypasses the 8432.

Adding a ball valve in the cooler line allows forcing all flow to the bypass port. That results in fast warmup, but won't help a hot oil problem. When fighting "too hot", installing a viscosity valve and removing the vernatherm is mostly just a way to check the latter. If it cools well, the vernatherm was not extending to close the bypass.

That makes sense, thanks!

Going a little off-topic to the original thread, I have the Lycoming filter adapter (77852) and I think I read somewhere that the vernatherm and spring/plunger could be installed at the same time?

I wanted to give the spring/plunger a shot to see if it helped reduce my oil temps. Unfortunately I didn't read about/think to do this until I just changed my oil. Literally two days ago, haha.

I looked at it pretty closely and was hoping that because of the design of the lycoming adapter that installing the spring/plunger would merely isolate the vernatherm and not cause the two devices to interfere with each other. Otherwise I'm probably going to end up spilling a bunch of brand new oil to install a vernatherm plug.
 
Going a little off-topic to the original thread, I have the Lycoming filter adapter (77852) and I think I read somewhere that the vernatherm and spring/plunger could be installed at the same time?

Some filter adapters (like the ECI in post 15) seat the vernatherm tip directly into the accessory case bypass hole ("from pump", post 11), which means the tip of the vernatherm can foul the plunger.

Others (including the Lycoming AC-style, post 1, and the Superior adapter, post 6) seat the vernatherm into a bypass hole in the adapter casing, thus the plunger and vernatherm can't foul.
 
Some filter adapters (like the ECI in post 15) seat the vernatherm tip directly into the accessory case bypass hole ("from pump", post 11), which means the tip of the vernatherm can foul the plunger.

Others (including the Lycoming AC-style, post 1, and the Superior adapter, post 6) seat the vernatherm into a bypass hole in the adapter casing, thus the plunger and vernatherm can't foul.

Ok, back to the topic here then - the best I can tell, with the type of oil filter adapter I have (pictured in your first post) installing the spring/plunger isolates the vernatherm's upper "direct from oil pump" cavity unless the spring/plunger bypasses for any reason. So at least in high OATs, I think I can have both installed and not see any issues - I think it should perform as if there's only a spring/plunger in there.

I'm going to give it a shot, I know a guy that has a set leftover from his engine he may loan me to test with. Isolating the vernatherm's functional cavity in the filter adapter should show if there's any problems there. I've gone through every other part of the oil cooling system except replacing the hoses themselves, which appear unobstructed when looking through them.
 
<<My engine has what this picture shows as "oil plunger". Is that a vernatherm?>>

No. Most likely it is just a plug, but it may have a spring and plunger installed under the plug. If so, remove the spring and plunger.

Lycoming%20Oil%20Cooler%20Bypass%20Plunger.jpg


The spring and plunger can best be described as an historical remnant. They date from the days before Lycoming's introduction of the vernatherm. Here is a page from Lycoming SI-1008B, circa 1966.

Lyc%20SI%201008B%20Vernatherm%20Install.jpg


In the pre-vernatherm days all oil went to the cooler, all the time. The spring and plunger served as a pressure relief bypass in the event oil cooler flow became blocked. The introduction of the vernatherm made the spring and plunger unnecessary; the vernatherm has both a thermostatic plunger and a pressure relief spring.

Important note: take a close look at the cutaway drawing in the upper right of the 1008B illustration. If you're using an old-fashioned oil screen (unlikely) or a filter adapter with the vernatherm oriented like the old oil screen (your right angle adapter), it is possible for the tip of the vernatherm to foul the oil plunger if you have both installed in the same engine. There's another Lycoming SI addressing this issue.


Sorry for resurrecting a thread. I have a rebuilt PV IO-540. I know where the oil cooler line in an out should be, but on the back of my "thermostat valve assembly" (thermavern?) I have another 3/8 NPT port, which I am assuming is oil. It faces straight aft. Is this an alternate oil cooler in or out?

The engine came with plastic inserts for all three of those ports, so my assumption is it is intended for use.

Thanks
 
I believe the third port, you are referring to, in the back of the oil screen housing, should be the port for your oil temperature prob. If you are locating that in a different port you can just plug it.
Good Luck,
Mahlon
 
Remote oil filter

... and to revamp this thread once more:

Mine is a narrow-deck O-320 C3B of mid-1950's vintage. That means oil screen rather than filter, and not Vernatherm but rather the pressure relief valve.

Going with the schematic, this also means that all oil goes through the oil cooler. This goes well with the remark of the previous owner who mentioned that with the oil cooler being an O-360 unit, the engine runs a bit cool on the oil.

Now... I would like to add a proper oil filter and was wondering if I couldn't simply put a remote oil filter in the line going to the oil cooler. Something like this one: https://www.speedwaymotors.com/Single-Remote-Oil-Filter-Bracket-Ford-Filter,1164.html (or something a bit nicer and less China-ey)

Any comments?

Hans
 
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Mine is a narrow-deck O-320 C3B of mid-1950's vintage. That means oil screen rather than filter, and not Vernatherm but rather the pressure relief valve.

I would like to add a proper oil filter and was wondering if I couldn't simply put a remote oil filter in the line going to the oil cooler.

Increasing flow restriction along the cooler path would simply hold the viscosity valve open, bypassing both filter and cooler. It would either remain open all the time, or for some longer period of time during warmup.

As designed, the system places any screen or filter restriction after the cooler and bypass flows rejoin.
 
Dan, reviving this thread again to better understand something. How does the fuel pump plunger get oil? Is it just splash from the gears or is there a hole in the accessory case that feeds it?

Next question, am I correct in understanding that the only path for unfiltered oil from the pump is either to the oil cooler, filter adapter, or prop governor which in turn goes to main front bearing? No where else?

Just trying to visualize what happens with all the particles small enough to make it past the suction screen.

Thanks!
 
Dan, reviving this thread again to better understand something. How does the fuel pump plunger get oil? Is it just splash from the gears or is there a hole in the accessory case that feeds it?

Next question, am I correct in understanding that the only path for unfiltered oil from the pump is either to the oil cooler, filter adapter, or prop governor which in turn goes to main front bearing? No where else?

Just trying to visualize what happens with all the particles small enough to make it past the suction screen.

Thanks!

Since nobody took this one I reached out to Lycoming tech support. They confirmed splash lubrication on the fuel pump plunger and my understanding of the oil path was correct. Just thought I would post for any future readers! :D

P.S. I have always found Lycomings technical support very responsive!
 
Thx for the info

I added your experience to the engine section of my database. When I add oil, the funnel is conspicuously cleaned.
 
Oil to cooler at viscosity valve location "A"?

Dan,

Reviving this thread again...and first time poster.

I have a Lycoming IO-540C1B5 which has been modified to use the vernatherm, however, the "to oil cooler" line is run from location A instead of the normal location which is indicated as "B" in the manual page you posted from 1966.

Is location A acceptable or do I need to change the "to oil cooler" line to location B? Of note, your post is the only reference I've found with the verbiage indicating this as normal and acceptable on the bottom part of the page.

The engine was originally from a 1962 commanche, it is now finding a home in an RV-10.

Thanks,

Roy Wylie
 

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Dan,

Reviving this thread again...and first time poster.

I have a Lycoming IO-540C1B5 which has been modified to use the vernatherm, however, the "to oil cooler" line is run from location A instead of the normal location which is indicated as "B" in the manual page you posted from 1966.

Is location A acceptable or do I need to change the "to oil cooler" line to location B? Of note, your post is the only reference I've found with the verbiage indicating this as normal and acceptable on the bottom part of the page.

The engine was originally from a 1962 commanche, it is now finding a home in an RV-10.

Thanks,

Roy Wylie

As long as you have a vernatherm installed, A or B can be used. The unused hole must be plugged.

Larry
 
New schematic, modified oil system for manual control of oil flow through the cooler.

Allows complete blockage of all cooler flow in cold weather.

Guarantees max flow through the cooler in hot weather, i.e. no possible vernatherm wax capsule or tip seal failure.

Add a viscosity valve in the accessory case (plunger and spring in previous illustrations), remove the vernatherm, and add a ball valve to the cooler oil supply line.

Caveat; given really cold conditions and single weight oil, it is possible to thicken the stationary oil trapped in the cooler so much that it may not flow if the ball is subsequently opened. Not as likely with multigrade.
.
Lycoming%20Oil%20Schematic%20Viscosity%20Valve.jpg
 
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Larry Vetterman put me onto this setup years ago where you remove the troublesome vernatherm and add the oil cooler bypass spring and plunger along with a ball valve controlled with a push-pull cable. Works excellent. Thanks for the diagram Dan! Good stuff.
 
Anyone happen to have part numbers & supply sources for this ball valve arrangement?

My OT remains too low (in my opinion) and thus I am considering either the ball valve or the oil cooler shutter strategy. I suppose the shutter is one less component "internal" to the engine.

Prior to either, I need to ensure that the vernatherm isn't somehow failed extended.
 
Dec 2017

Thanks Dan & Jim. I should have mentioned that I had the viscosity valve parts list from your previous posts.

I found this example in a Dec 2017 article in Sport Aviation about this subject.
 

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New schematic, modified oil system for manual control of oil flow through the cooler.

Allows complete blockage of all cooler flow in cold weather.

Guarantees max flow through the cooler in hot weather, i.e. no possible vernatherm wax capsule or tip seal failure.

Add a viscosity valve in the accessory case (plunger and spring in previous illustrations), remove the vernatherm, and add a ball valve to the cooler oil supply line.

Caveat; given really cold conditions and single weight oil, it is possible to thicken the stationary oil trapped in the cooler so much that it may not flow if the ball is subsequently opened. Not as likely with multigrade.
.
Lycoming%20Oil%20Schematic%20Viscosity%20Valve.jpg

Thanks for the updated diagram, Dan!

I thought that if you ran the spring and ball (type I bypass?) that you could just leave the vernatherm in place. My (feeble) memory told me that the type I bypassed the type II if they were both installed, not allowing the type II to do its job. I think there was a note about it in an engine manual?
 
I thought that if you ran the spring and ball (type I bypass?) that you could just leave the vernatherm in place. My (feeble) memory told me that the type I bypassed the type II if they were both installed, not allowing the type II to do its job. I think there was a note about it in an engine manual?

The warning is in the the SB posted above.

Housings which position the vernatherm tip directly into the accessory case bypass hole may allow the tip to foul the plunger. Snip below.
.
 

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