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Don't drive in a rear main seal too far!


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I just learned this the hard way putting my 2.5L back into our '98OBW last night. I had pulled the motor a week ago as a result of the usual head gasket problem and had the heads checked over by a machine shop. The rear main seal wasn't leaking, but I figured I'd replace it since "I was in there." Well, I apparently wasn't paying too close attention to the depth of the original seal and drove the new seal in way too far. I didn't realize there wasn't anything to stop it from going in too far. I didn't think much of it at the time, but I think I drove the new seal in about half an inch passed flush. It should be sitting much closer to flush, like 1/16" in or so.

 

The result? A great running motor with new updated multi-layer steel headgaskets--and a whopper of an oil leak coming from the back side :headbang: .

 

Luckily, pulling the motor again only took 2 hours because it was so fresh in my mind and I left the intake assembly on the engine. I should have the engine back in, AGAIN, in a few hours....

 

Make sure to learn from my mistake!

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I pushed mine a little too far also:eek: , but not much. No leak yet, but I'm crossing my fingers. That's about a month ago.

 

I noticed on mine after removing the seal I drove in too far that not only was there nothing to stop it from going in too far, but there were two changes in diameter of the crank surface visible through the opening there (in other words, the crank got more narrow via 2 step changes the further in you went). I must have drove the seal in to the 1st diameter change and the seal was not making good contact. It was obvious that it was leaking around the inner crank sealing surface and not the block sealing surface.

 

I put the motor back in yesterday with the second new seal, let it idle for an hour as I cleaned up the mess I made in the garage, and took it for a test drive. No more leaks--whew! This is the first seal I've seen on several engines I've worked on that you can actually drive it in too far. The Haynes manual only mentions setting the seal to the depth of the previous one. Well, what if the previous one wasn't set correctly....

 

There's nothing to even keep the seal to be driven in straight in the first place. Both new seals that I drove in didn't want to be driven in perfectly flush. I had to tap at alternating spots because it kept going off-kilter.

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I noticed on mine after removing the seal I drove in too far that not only was there nothing to stop it from going in too far, but there were two changes in diameter of the crank surface visible through the opening there (in other words, the crank got more narrow via 2 step changes the further in you went). I must have drove the seal in to the 1st diameter change and the seal was not making good contact. It was obvious that it was leaking around the inner crank sealing surface and not the block sealing surface.

 

I put the motor back in yesterday with the second new seal, let it idle for an hour as I cleaned up the mess I made in the garage, and took it for a test drive. No more leaks--whew! This is the first seal I've seen on several engines I've worked on that you can actually drive it in too far. The Haynes manual only mentions setting the seal to the depth of the previous one. Well, what if the previous one wasn't set correctly....

 

There's nothing to even keep the seal to be driven in straight in the first place. Both new seals that I drove in didn't want to be driven in perfectly flush. I had to tap at alternating spots because it kept going off-kilter.

 

Yes, the large diameter of this seal makes it specialy difficult to drive in correctly without much experience and the right tool. I had neither so the seal is slightly pass were it should be (but not pass the point where the crank diameter changes I think) and very very slightly crooked. I thing I should cross all of my fingers...

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The nice part is, this motor is VERY easy to remove and I think Subaru actually put some thought in it? I'd rather they had put some of that "thought" into better headgaskets, but oh well.

 

Anyway, I didn't believe boardmember grossgary when he said he removed this type of motor in 2 hours. When I had to pull the engine the second time for the main seal leak, I got it out in 1 hour 50 minutes. Reinstallation took about 2.5 hours due to having to use the torque wrench and clean things and slowly burp the cooling system during filling.

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