Flywheel housing O ring

[rejeep]

what exactly does this O ring do?
I am ready to swap my engine but I dont think I have a new one to put in.. is it so horrible to resuse the old one.?

[SafeAirOne]

It prevents oil from leaking out of the rear main bearing cap area to the surface between the flywheel housing and block. I'd change it.

I think I have 2 spares that came with my 2.5 bottom end gasket kit (my version of the 2.5 doesn't use this o-ring. If you want them, PM me your address.

[EDIT:]

Just to be sure we're talking about the same thing, it's # 15 here:

[rejeep]

i think so.. its sits in the groove in the flywheel housing..

I am about to start my engine swap and im a bit confused as to how everything is removed/installed..
the green bible is great in certain aspects, but lacks some details in others..

Should that O ring be installed with a bit of grease to keep in place or dry?

[SafeAirOne]

Should that O ring be installed with a bit of grease to keep in place or dry?

Can't say for sure--My engine uses a paper gasket and anerobic gasket sealant instead of the o-ring. I'd think a new o-ring would fit pretty snugly in the groove. I doubt that some grease or petrolatum will do any harm if you need to stick a new o-ring to the groove.

Becasue of deformity, I probably wouldn't use the old gasket.