Rear Main Seal / 2.5 Iron Duke (Page 1/2)
82-T/A [At Work] MAY 10, 12:48 PM
Can anyone tell me which "direction" the Rear Main Seal should be pressed in?

I know it's directional in order to direct the oil back into the block, and that the crank turns clockwise from the front, which I assume to mean counter-clockwise in the back.

The rear main seal (new one) is hollow on one side (exposing the seal-spring), and closed on the other. I can't find anything that tells me which way it should be pressed in.


Thank you!
cartercarbaficionado MAY 10, 04:16 PM

quote
Originally posted by 82-T/A [At Work]:

Can anyone tell me which "direction" the Rear Main Seal should be pressed in?

I know it's directional in order to direct the oil back into the block, and that the crank turns clockwise from the front, which I assume to mean counter-clockwise in the back.

The rear main seal (new one) is hollow on one side (exposing the seal-spring), and closed on the other. I can't find anything that tells me which way it should be pressed in.


Thank you!


hollow side faces crankshaft pulley 99% of the time for the rear main will look at my 84 iron duke at some point to tell you if it's different than everything else
jelly2m8 MAY 10, 05:25 PM
Open/ spring side inwards.
Patrick MAY 10, 06:39 PM

quote
Originally posted by 82-T/A [At Work]:

The rear main seal (new one) is hollow on one side (exposing the seal-spring), and closed on the other. I can't find anything that tells me which way it should be pressed in.



The only application that I've ever been aware of where an engine's rear main oil seal was mounted "backwards" was on a water pump. We installed two rear main oil seals on those engines... the inner one was installed the regular way, and the outer one was installed "backwards", to assist in preventing water from being forced past the regularly mounted oil seal and into the crankcase.
82-T/A [At Work] MAY 10, 08:40 PM
Thanks Jelly, I appreciate it... that makes sense. It concurs with my timing cover seal, which also did not have any instructions and I had to "assume."

And Patrick... in this case, there's nothing obvious to tell me which direction it gets pressed in. It could literally go in either way. It should be relatively obvious, but no arrow or anything... not even instructions, which I find totally weird.
Patrick MAY 10, 09:35 PM

quote
Originally posted by 82-T/A [At Work]:

And Patrick... in this case, there's nothing obvious to tell me which direction it gets pressed in.



The "obvious" indication is that the seal-spring goes (as far as I know, always) on the pressurized side.
82-T/A [At Work] MAY 10, 09:44 PM

quote
Originally posted by Patrick:

The "obvious" indication is that the seal-spring goes (as far as I know, always) on the pressurized side.



I'm not sure what you mean... the seal-spring is dead smack in the middle... it's just that one side of the seal is open, the other side is closed. But it would seal it regardless of which direction you pressed it in... but the flap that the spring holds down has little /////// on them which are designed to carefully guide the oil back into the engine... and that really dictates which way it should be properly pressed in (otherwise it'll fail quickly).

It would make sense to me that the open side should be in, but I've never read anything that told me so...

... it's exactly the opposite of a freeze plug of course, in which the open side goes out, and the closed side goes into the block... lol.


olejoedad MAY 10, 09:57 PM
Todd, you're supposed to pay attention to those things when you tear it apart.....
82-T/A [At Work] MAY 10, 10:18 PM

quote
Originally posted by olejoedad:

Todd, you're supposed to pay attention to those things when you tear it apart.....




Joe, we've torn the ENTIRE car apart. We took 100s of pictures. Every screw was bagged and labelled, and lots of pictures... and tons of manuals, but this one thing wasn't covered in any of the manuals.

... I guess we DO technically have a video of it...




But shoot you guys are a tough crowd. I appreciate that you guys think so highly of me that you expect me to know these answers already... but I took a 14 year hiatus from working on cars. I'm ok looking like a complete idiot so long as everything gets done properly. Anyway, I wouldn't have asked... but I searched literally everywhere, and this was the closest thing I could possibly find that even slightly gave me an answer... https://www.scegaskets.com/...r-Main-Seal-Inst.pdf

... and that's for a two-piece rear main seal that doesn't get pressed in.
Patrick MAY 11, 02:06 AM

quote
Originally posted by 82-T/A [At Work]:

...but this one thing wasn't covered in any of the manuals.



Google is your friend - Which way is a crankshaft oil seal installed?