Hopefully a simple question here. Without tearing things apart, is there a way to confirm whether a small oil leak is coming from the rear main seal or is just a leak at the rear of the oil pan?

A few years ago, I dropped the pan to install a baffle. Upon reinstallation of the pan and driving around a bit, I noticed a small leak was coming from the very back of the pan where there's a "rectangular hole" between the pan and bellhousing. I figured my pan install was botched. Fast forward a couple years, I dropped the pan again to upgrade my AP1's oil banjo bolts. This time I was meticulous about reinstalling the pan - used honda HT sealer, torqued all bolts to exact spec, etc. But the result was same thing - a very small drip on the garage floor. It might seem like a main seal leak but it was a heck of a coincidence that the leak started the first time I reinstalled the pan.

I've heard that a main seal leak will fling oil everywhere around the bellhousing - but do our S2000's have an inspection plate??

 

Quite often those kind of leaks start higher up, they just come out at that location due to gravity and the angle of the drivetrain. I had drips in that location quite a bit and they all came from higher up. Sometimes it happens if you spill a few drops of oil on the valvecover when filling the oil fill hole, and I was always adding oil on my Ap1. It could be a valvecover leak too.

 

I'd definitely inspect the valve cover gasket first if it hasn't been done already. How many miles on your car? It's extremely rare to come across a bad rear main seal on these cars, even at very high mileage. When I upgraded my clutch on an otherwise bone-stock (at the time) 02 with only 53k miles on it a few years ago, the rear main seal was in perfect shape, so much so that I didn't bother messing with it. I wouldn't touch a rear main seal unless it was visibly weeping/leaking, even if the car was high mileage.

In addition, I've had to remove/replace the oil pan on my car on 2 separate occasions; once when I was upgrading to the Toda baffled pan, and the second time when I dropped a keeper down an oil galley when upgrading my springs and retainers and had to drop the pan to retrieve it. Didn't have a leak either time.

As stated above, check that valve cover gasket.

 

take your bare dry hand and rub it on the back of the head by the firewall, touch the rear of the valvecover, head, and block as far as you can reach, and look for wet oil . I know when I spill a few drops of oil when filling the engine with oil it goes onto the coil cover and then the oil drips into the valvecover underneath and it comes out the back side of the valvecover by the firewall, it then drips down to the exact spot you mention at the square opening.

 

I've done the same thing. Drips caused from this sort of thing will stop in a few days. So, that is a factor. I have started to wrap a towel around the valve cover where the funnel inserts so that nothing I spill ever hits the motor.
How many mile on your motor OP?

 

Thanks for the tips. I'll check the back of the engine for drips higher up.

My Ap1 has 39,000 miles. The drip was first noticed about 10,000 miles ago.

 

Seems to me that, while possible, a rear main seal leak is not likely at that mileage.

Did it first start when you did something to the motor like oil change, remove valve cover, make a mod, anything like that?

Does it leak consistently? Or does the leak stop, and then start up again?

Can you tell if the leak originates from inside the bell housing v. on top of the bell housing?

Might help to get it up on a lift and see if that improves your ability to see the source.

Chasing down oil leaks can be a real PIA. Good luck with it.

 

He said it started when he removed oil pan (to add a vaffle). But when he had to remove pan again much later, he went all in on curing the leak he assumed was pan gasket. But leak persists.

It occurs to me doing the pan both times involves plenty of opportunity to spill oil while adding it. We know such spilled oil can end up leaking down the back and mimic rear main seal.

So I have the same questions about how consistent these leaks have presented during all this time.

 

It seems like too much of a coincidence to have the rear main seal on a low mileage motor start to leak at the very same time that the oil pan was removed.
I bet dollars to donuts there is either some oil spilled when filling the motor or a pan leak caused when pan was removed and re-installed.

 

Maybe the deal is pan gasket 1 really did leak, then pan gasket 2, with its all-in making sure it sealed did NOT leak, but then oil got spilled during refill, which mimicked the original leak.