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Lycoming oil flow

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bdespins(at)telusplanet.n
Guest

Posted: Wed Jul 05, 2006 6:03 am Post subject: Lycoming oil flow

I'm trying to figure out how the oil system in my Lycoming O-540 works.  

I know there is a great deal of variability between models, but I  

wonder if someone can help me make sense of what I've found.  From the 

back of the sump, there is an finger screen in the oil pickup tube and 

from there the oil goes up to the pump.  From the pump it goes to two 

possible places, oil cooler or oil filter.  Lets assume the oil is cold 

and the vernitherm (located next to the oil filter assembly) is open.  

Since it is open, oil flows past the vernitherm and onto the outside 

surface of the filtering element inside of the oil filter.  It returns 

down the middle of the filter and goes to the right side oil galley.  

This is the location of the oil pressure valve which regulates pressure 

by dumping any excess to the sump.  If the oil is getting hot, the 

vernitherm closes and more oil is forced from the pump into the oil 

coolers.  The return from the coolers is into the left side oil galley. 



This is all the information I can deduce from the exterior of the 

accessory case.  I'm sure there are more details that I'm missing.  For 

example, it would seem that only the right galley gets filtered oil and 

only the left galley get cool oil.  My attempt at describing the system 

also seems to imply that oil is either filtered or cooled but not both 

at the same time.



Can somebody please assist me in filling in the missing passages and 

make sense of all this?



Thanks.

Bernard Despins

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glcasey(at)adelphia.net
Guest

Posted: Thu Jul 06, 2006 5:03 am Post subject: Lycoming oil flow

Appearances can be deceiving.  The oil flow order is:  Inlet screen, pump, vernatherm and cooler in parallel, filter, relief valve and then to the right and left side headers.  The feeds for the vacuum pump, AN fuel pump and hydraulic pump drives are taken off ahead of the relief valve and all the other functions are taken after the valve.  According to the book this is true of all 4 and 6-cylinder engines, including, I believe, the aerobatic engines - the internal oil sump is just replaced by an external oil tank.

Gary Casey



On Jul 5, 2006, at 11:56 PM, Engines-List Digest Server wrote:

 	  Quote: 	
		  

I'm trying to figure out how the oil system in my Lycoming O-540 works.   

I know there is a great deal of variability between models, but I   

wonder if someone can help me make sense of what I've found.  From the  

back of the sump, there is an finger screen in the oil pickup tube and  

from there the oil goes up to the pump.  From the pump it goes to two  

possible places, oil cooler or oil filter.  Lets assume the oil is cold  

and the vernitherm (located next to the oil filter assembly) is open.   

Since it is open, oil flows past the vernitherm and onto the outside  

surface of the filtering element inside of the oil filter.  It returns  

down the middle of the filter and goes to the right side oil galley.   

This is the location of the oil pressure valve which regulates pressure  

by dumping any excess to the sump.  If the oil is getting hot, the  

vernitherm closes and more oil is forced from the pump into the oil  

coolers.  The return from the coolers is into the left side oil galley.  



 

This is all the information I can deduce from the exterior of the  

accessory case.  I'm sure there are more details that I'm missing.  For  

example, it would seem that only the right galley gets filtered oil and  

only the left galley get cool oil.  My attempt at describing the system  

also seems to imply that oil is either filtered or cooled but not both  

at the same time. 



 

Can somebody please assist me in filling in the missing passages and  

make sense of all this? 



 

Thanks. 

Bernard Despins

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mcculleyja(at)starpower.n
Guest

Posted: Thu Jul 06, 2006 7:30 am Post subject: Lycoming oil flow

The path of the oil is correctly described up to the point where you

stated "return from the coolers is into the left side oil galley".



The return from the cooler follows the same path as does the oil when

cold and not passing through the cooler. It goes from the pump to the

outside of the oil filter element either directly from the pump or as

return oil from the cooler to the outside of the filter. The path is

determined by whether the vernatherm valve is on its seat or not. After

the oil passes through the filter it goes directly to the right oil

galley where it passes the pressure sensor port, the oil pressure relief

valve and a crossover channel to the left oil galley.



Actually, while the oil is still cold it can flow in parallel paths

through both the cooler and also the more direct path through the open

vernatherm valve. The path of least resistance is automatically via the

direct route and not the higher resistance path through the cooler. As

the oil heats, the vernatherm slowly closes completely, forcing all the

oil to take the higher resistance path through the cooler. This

modulated flow path thus regulates the temperature during periods when

only partial flow through the cooler is appropriate to maintain desired

temperature.



There is no difference in the oil flow path through the oil galleys and

all the bearings due to the vernatherm. The only difference is

whether the oil is forced to flow partially or completely through the

cooler before continuing through the engine.



The path can best be seen by studying the accessory case when it is not

installed on the engine. External views of the installed case can easily

deceive one!



Jim McCulley

------------------------------------------------------------------------

Time: 07:03:39 AM PST US




<bdespins(at)telusplanet.net>



I'm trying to figure out how the oil system in my Lycoming O-540 works.

I know there is a great deal of variability between models, but I

wonder if someone can help me make sense of what I've found.  From the

back of the sump, there is an finger screen in the oil pickup tube and

from there the oil goes up to the pump.  From the pump it goes to two

possible places, oil cooler or oil filter.  Lets assume the oil is cold

and the vernitherm (located next to the oil filter assembly) is open.

Since it is open, oil flows past the vernitherm and onto the outside

surface of the filtering element inside of the oil filter.  It returns

down the middle of the filter and goes to the right side oil galley.

This is the location of the oil pressure valve which regulates pressure

by dumping any excess to the sump.  If the oil is getting hot, the

vernitherm closes and more oil is forced from the pump into the oil

coolers.  The return from the coolers is into the left side oil galley.



This is all the information I can deduce from the exterior of the

accessory case.  I'm sure there are more details that I'm missing.  For

example, it would seem that only the right galley gets filtered oil and

only the left galley get cool oil.  My attempt at describing the system

also seems to imply that oil is either filtered or cooled but not both

at the same time.



Can somebody please assist me in filling in the missing passages and

make sense of all this?



Thanks.

Bernard Despins

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noelloveys(at)yahoo.ca
Guest

Posted: Thu Jul 06, 2006 4:40 pm Post subject: Lycoming oil flow

I just happened to have a  squint at the AVCO Lycoming overhaul manual today.  One of the things I was  looking up was the oil flow diagram.  It is exactly as you described it  including the A engines.

  

  

 

Noel [quote]   

   --

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