1996 4Runner, 254,000 miles has developed an oil leak. I thought it was valve cover gaskets, but have replaced those and it's still leaking. Oil drips from back between transmission and motor. Are there any oil sending units back there or something else that could be causing this leak? Thinking it might be the main seal? It's oil, not transmission fluid. Really driving me nuts!

 

My guess is also prolly main seal if it's not the head gasket, good luck report back!

 

If the back of the engine is dry above the bellhousing (hard to see) and oil is coming out of the bellhousing, it's almost certainly the rear main seal.

Before yanking the trans, however, I'd check the PCV valve and associated crankcase ventilation piping. If those get gummed shut, the blow-by fumes will find *some* way to get out, usually pushing their way through a seal. If there's a ventilation issue and you fix it, the oil leak will very likely stop.

 

There's also a rubber coated plug at the rear of each cylinder head that corresponds to the camshaft seal at the front of the head. I have found them leaking several times. You can get a replacement plug from a dealer and replace it fairly easily when the valve cover is off. It's held in place by a brace bolted to the head. The camshaft bearing cap that sits over it doesn't actually contact the cam so there's no worry about taking it off.

 

There are circular cam plugs and often missed half-moon plugs that should also be looked at. The half-moon plugs sit low were oil will pool and have been cited as one of the known leak sources. This thread has good pictures of both:

http://www.toyota-4runner.org/3rd-ge...-s-n-pics.html

My '98 ltd has developed a leak back there on the drivers side, and while it is small enough to ignore it drips right on the hot exhaust. Smells like I am carrying around a bucket of hot roofing tar. When I deal with it, I will probably get one of the ebay kits so I can replace the pcv and grommet, spark plugs, wires, and maybe even have my injectors cleaned too. Why spend all that time and not do it all?

As a stop-gap measure, has anyone tried just cleaning the area and smearing sealer on the outside? Seems like it could work.