Lycoming Accessory Case Removal and Oil Pump

I am going to remove my accessory case on an IO-540 to inspect the oil pump.

With respect to this subject...can you all PLEASE share with me some tips/tricks/experience/gotchas/ I wish I woulda...couldas/ well wishes/ mental telepathy moments of silence/ good fortune dances/ etc?!?!?!

Of course I have a service manual but there is always more to it than that...

THANKS!!!

The idlers gears/magneto gears are held on by the accessory case, so if you have the engine mounted on a tail dagger and you pull the accessory case off, the gears will fall off. Maybe mark the gears with a sharpie just in case they do fall off while you are working on it.

Just out curiosity, what's wrong with your oil pump?

Hard to reach bolt

The hard to reach bolt under one of the gears typically can be removed by a cylinder base wrench

Also, engine work requires the parts manual in addition to the service manual

Use a knife/razor blade to make a clean slice in the sump gasket. Should make it easier ti get a clean seal when reinstalling case.

bring engine to TDC / compression stroke on #1, so you can observfe the marks on the crank, cam and idler gear before removing the idler gear. them. It seems some gears have the marks worn away and if that's the case you'll need to make marks. Best to figure this out before pulling the idler gear out. Better yet, don't remove it. No need to pull it out, as the oil pump is attached to the back of the accy case.

YOu will need to match up the sockets/prongs on the oil pump to crankshaft meshing when reinstalling. Best to get this all lined up before applying sealant and gaskets.

Larry

>The idlers gears/magneto gears are held on by the accessory case, so if you have the engine mounted on a tail dagger and you pull the accessory case off, the gears will fall off. Maybe mark the gears with a sharpie just in case they do fall off while you are working on it.

The engine is out of the airplane.

I am about to pull the accessory case...are not the gears supposed to remain on the crankcase???

This overhaul video shows the gears being installed on the engine first and then the accessory case is lowered onto the crankcase (of course the engine is vertical.

>Just out curiosity, what's wrong with your oil pump?

I need to inspect the oil pump for AD compliance.

Vans101 said:

I need to inspect the oil pump for AD compliance.

Click to expand...

I had to do that as well. The engine log showed the wrong P/N gears were installed. So I removed the engine from the aircraft (PITA) and delivered it to the mechanic. He removed the sump, accessory case and the oil pump cover, only to find that the gears were the correct part numbers after all. Months of work for nothing...

Vans101 said:

>The idlers gears/magneto gears are held on by the accessory case, so if you have the engine mounted on a tail dagger and you pull the accessory case off, the gears will fall off. Maybe mark the gears with a sharpie just in case they do fall off while you are working on it.

The engine is out of the airplane.

I am about to pull the accessory case...are not the gears supposed to remain on the crankcase???

This overhaul video shows the gears being installed on the engine first and then the accessory case is lowered onto the crankcase (of course the engine is vertical.

>Just out curiosity, what's wrong with your oil pump?

I need to inspect the oil pump for AD compliance.

Click to expand...

crank and cam gears are secured to respective shafts. Idler gears just sit on small protrusions on the block and pads on the accy case prevent them from falling off. Once the accy case is off, it is possible to pull off the idler gears and they will likely fall off if the block in inclined to the rear.

Given that the engine if off the plane, you may want to consider pulling the oil sump before the accy case. This will make removal a lot easier if you have never done it before. There are two alignment pins that require the cover to come straight off for about 1/4" and you will likely have a gasket that resists letting go. The sump gasket will be the issue, as you must force it to break the seal sideways.

Larry

Loosen the first two bolts in front of the accessory parting surface on the sump. This will allow a bit of play in the sump when reinstalling the acc case and not pinch the sump gasket. Although if its out of the aircraft no biggie to take the sump off. If not taking the sump off, in addition to loosing those sump bolts, I always pull the dowels out of the crankcase, before reassembly, and ream the holes in the acc case to 5/16 all the way through and then reinstall the dowels with a bit of locktight after re-mating the acc case to the engine, before tightening the mounting bolts.
Good Luck,
Mahlon