Lycoming Accessory Case Oil Schematic

[DanH]

Resurrecting this thread to ask "how to get the plunger out of the hole?" I have taken out the plug and the spring but the plunger is stuck and/or held down by gravity. The side of the plunger is visible through the hole in the accessory case in the centre of the housing for the pressure screen or filter adapter.
My magnetic pickup tool won't fit down the plunger hole but maybe compressed air in one of the ports will blow the plunger out?

Thanks for any hints!

Disconnect the oil cooler hose at the port marked "out to cooler". Shoot compressed air into the port. It will probably pop the plunger up, at least until the air can escape through the bypass port (hold a rag over it, as it may spit oil). Freed up, the magnet may then work.

If air doesn't move it, hydraulic pressure will, but let's try a shot of air first.
Ca

 

[Toobuilder]

Short of getting a smaller magnet to grab the piston (always works for me), a slightly less messy method might be to disconnect the upper hose from the cooler and shoot a bit of air into the “out” nipple on the cooler. Hydraulically, it’s the same as disconnecting the hose at the case as in the above suggestion.

 

[PaulvS]

Disconnect the oil cooler hose at the port marked "out to cooler". Shoot compressed air into the port. It will probably pop the plunger up, at least until the air can escape through the bypass port (hold a rag over it, as it may spit oil). Freed up, the magnet may then work.

If air doesn't move it, hydraulic pressure will, but let's try a shot of air first.
CaView attachment 64890

I tried compressed air @ 90 psi into the "too cooler" port and could hear gurgling in the sump but the plunger did not budge. Next, heating the accessory case with a hot air gun and applying WD40 didn't seem to make any difference.

It came out eventually by using a pop stick through the central port to push up the plunger from the side with the pop stick engaged in the plunger's groove. The plunger then got stuck a bit higher up in the cylinder and I managed to grab it and work it free with a tapered wedge pushed/pulled from above.



The plunger has some scoring on the sides that possibly made it more difficult to remove than is normal.



Thanks for the suggestions. I could've also tried a smaller strong magnet but the nearest town with a store is a 2 hour round trip...

 

[Toobuilder]

That plunger looks pretty scored up. What does the bore look like?

 

[PaulvS]

That plunger looks pretty scored up. What does the bore look like?

The bore is also similarly scuffed/scored, though the seat is OK.

I'm actually removing and discarding the spring and plunger and also the pressure screen housing, to be replaced with an adapter for a spin-on oil filter and vernatherm (per Lycoming SSP 885-2).

 

[Toobuilder]

If you were closer, I'd ask that you "discard" those items in my direction... Those springs are outrageously priced and the piston would probably clean up enough to be functional.

That said, dont be too quick to discard those items. The piston is generally much better at forcing oil through the cooler than a vernatherm and you may find that reinstalling it serves as a good troubleshooting item (or a solution) to high oil temps if you have them. I started running the piston as a means to prep the engine for summer temps but now run it year round. The vernatherm is completely bypassed in my engine.

 

[PaulvS]

If you were closer, I'd ask that you "discard" those items in my direction... Those springs are outrageously priced and the piston would probably clean up enough to be functional.

That said, dont be too quick to discard those items. The piston is generally much better at forcing oil through the cooler than a vernatherm and you may find that reinstalling it serves as a good troubleshooting item (or a solution) to high oil temps if you have them. I started running the piston as a means to prep the engine for summer temps but now run it year round. The vernatherm is completely bypassed in my engine.

I was in two minds about making the change to the oil system. Somebody gave me the adapter and the idea of an oil filter in place of the old pressure screen was appealing. But there was the added cost of a new vernatherm, plus the fittings and the hose to the oil cooler need changing due to interference with the housing.
I noticed that the price of the Lycoming pressure screen housing is over $1000!
I will hang onto the old parts at least until I know that the new system is working properly. The vernatherm seems to be potentially problematic, based on some postings on VAF.