SUBARUPictures of how I Replaced the leaky Oil Separator Plate and Rear Main Seal on the Subaru Legacy Outback 2.2 engine.


The Oil Separator Plate is on the rear of the engine, hidden behind the flywheel. It doesn't hold in the oil. Originally designed in plastic, which leaks. Then redesigned in aluminum, which leaks. Then redesigned in steel, which so far isn't leaking, knock on wood.

But first, lets pay some bills:

  1. Back of engine is oily from a leak. The oil leak is from the from the oil separator plate. The Rear Main Seal (RMS) and the transmission input shaft seal both look good. I will change the oil separator and the RMS while I am in here.
    Subaru oil leak in the oil separator plate

  2. I removed the oil separator plate and cleaned the mating surface with a plastic dish washing scrubber.
    Oil Cleaned

  3. Here is the new oil separator plate complete with subaru part number. $25 from the dealer with new bolts. This is the third redesign. The first was plastic, the second aluminum, and this one is steel.
    New Plate

  4. The new plate installed, using Permatex high temp RTV silicone gasket, and blue thread lock (I think I should have used the anaerobic here, same as on the oil pump). The odd bolt with thread lock already installed went into the top left hole with the arrow. Bolts use 4mm allen. Had to scramble to find one as the threadlock was drying.
    Plate Installed

  5. Removing the rear main seal. Installed new one using a block of wood and rubber mallet to seat it. I read in a motorcycle repair guide that all seals need grease on the inside of the seal before installation. The Subaru service manual says, "Install oil seal." All I did was use a tiny bit of clean oil to help it slide in. I will have to wait and see how it works.
    Rear Main Seal

  6. Next I sold out to make 02ยข so I can fulfill my lifelong dream of owning a 1986 944 with blown head gaskets.

    But no minivans!

  7. Then I finished my beer.

EDIT: 6/07
It has been 3 months and all looks good! However, it looks like there is another leak coming from the oil pan. Oil is blowing back from the oil pan, to the bottom of the flywheel, onto the exhaust, and onto the transmission. There is much less oil, so it is likely that the rear main seal and / or the separator plate were also leaking. They are notorious for leaks. But we all know that everything leaks on a Subaru. This oil pan leak is on my to do list.
EDIT: 10/07
7 months. Cam looks good. Water pump looks good. Oil pump looks good. No leaks there. All is dry and slightly dusty.
There is no burning oil on the exhaust. So that is way better, but:
The oil pan is slightly oily around the seal. There is a small amount of oil under the flywheel, just behind the oil pan. The oil is black and dry, so the leak is very slow. But it still has the potential to get blown into the bell housing and onto the clutch. AGAIN. We're in an apartment right now and can't dig into it. We will wait and see.
EDIT: 11/09
Over two years since change. Just changed the leaking oil pan gasket. Impossible to tell if the RMS or separator is also leaking. They are just too close together. Maybe if the oil pan leak is fixed, I will be able tell if there is a leak coming from somewhere else.
EDIT: 2/10
Three months since I changed the leaking oil pan gasket. All is dry and a bit dusty. Really. A subaru with no oil leak. I know. It's crazy.
EDIT: 11/14
The oil pan is mostly dry. Everything everywhere else is oily. Sigh.

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Last modified: 11/21/2014