I have a 2001 F150 Supercrew 4x4 Lariat. It has a small oil leak at the rear of the engine. The rear main seal looks good. So do the valve cover gaskets. The leak is closer to the passenger side, leaking down onto the starter then down to the pan where it drips to the ground. What's on the back side that leaks?

 

My first guess would be that the oil filter gasket is leaking. A small piece off crud on the mounting flange is enough to distort the gasket and cause a minor leak. If it is a big leak, still check the oil filter as the gasket could be skewed or the old gasket maybe was left in place, which could cause total sudden loss of oil at some point. Finally the filter can could have a seam leak.

 

You didn't mention what engine you have. I'm going to ASSUME you have a V8. The 5.4 is known to have issues with the passenger side head gasket at the rear of the head near the #3, #4 cylinders. It will leak as you describe. I don't know if the 4.6's were prone to the same thing. If you search in the 4.6-5.4 modular motor forum for head gasket leaks, you'll find plenty of posts about it.

 

Yes the 4.6L's have the leak also, I have a '99 4.6L and it has leaked since 63,xxx miles. Take it to the dealer to verify the leak and get your name on the recall list(if they ever have one, highly unlikely) You also may start smelling hot oil after long drives.....