Lycoming Accessory Case Oil Schematic

[svyolo]

Originally Posted by DanH

<<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.



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.



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

[mahlon_r]

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

[Lufthans]

... 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/Singl...lter,1164.html (or something a bit nicer and less China-ey)

Any comments?

Hans

[DanH]

Originally Posted by Lufthans

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.

[Lufthans]

Good point, makes sense. Thanks!