I recently installed a new clutch and 6-speed, so while I was in there I replaced the rear main seal. I was experiencing a bit of leakage from the previous seal, even though the engine had just been rebuilt. When I removed the flywheel I found the seal cocked in the bore, so it was no wonder there was a little leakage. I was absolutely meticulous installing the new one, oiled the lip, cleaned off the entire area with brake cleaner and a towel, tapped in the new seal going around the circumference with a large tap and hammer going easy with the hammer. Ran the car for 1000 miles without so much as a whisp of oil drip from the bellhousing drain hole. I ran a track event at Sebring last weekend, and today when I got under the car to do some work, I found some dripping from the bellhousing drain. Not a lot, but I should see any. The engine is naturally aspirated at this time, so the crankcase wasn't being artificially pressurized, and I had the PCV hooked up and a filter on the driver side valve cover nipple.

My question is have other people experienced consistent light leakage from that area, what would have again caused the new seal to become cocked in its bore (if it is in fact cocked again, I haven't pulled things to check), has anyone used sealant when installing a new rear main seal, like sealant around the outside of the seal?

Needless to say I am pissed right now and I really don't want to pull the transmission again.

 

I always put some high temp RTV around the outside edge of seals like that, no problems thus far.

 

1. are you sure it's engine oil?
2. did you wipe up all the old oil from inside the bell housing?
3. if you aren't sure it's engine oil it could be trans fluid, front main seal

 

Smelled like motor oil, did not smell like the GL5 gear oil in the tranny. I am going to check the CAS seal to make sure it's not leaking down onto the bellhousing, but it's only got a few thousand miles on it and it's the fancy x-ring unit from Miataroadster. The bellhousing was thoroughly cleaned before installation. The tranny was sparkling clean for 1000 miles and not a hint of any leak under the car, until now.

 

it could be lots of things. oil pan seal, valve cover gasket, cas...

 

Valve cover gasket is new. I'm not going to sweat it at this point. It's not enough to make any kind of dent on the dipstick. Maybe I had the pan a bit overfilled before the event and that was the result. I am going to check the valve cover gasket and CAS seal and then just monitor the situation.

 

Bad CAS O rings leak and drip from the bottom of the bellhousing.
Thats likely what it is.

 

I can only pray that is the culprit. Thanks.

 

that would be my suggestion as well.

 

Double check that it is not trans fluid. I had the font tranny seal leak and thought it was engine oil because it was black even though the fluid was brand new redline.

 

CAS for me too. Had the same thing happen. Looks for the world like rear main. Just a whole lot cheaper and easier, 20 minutes and $2. Fingers are crossed for you!

 

I ran my hand under the CAS, looked like enough oil was on my hand that it may be the source. The oil that came from the bellhousing was motor oil, not GL5 gear oil that is in the tranny. I didn't think it was the CAS seal since the one in the engine is only a year old.