This is on my buddy's truck. We replaced the oil pan gasket, the oil bypass plate gasket, and the drain plug gasket. He says it is still leaking! We took this pic before the work. Ignore the wet filter; we had just loosened it. Where else could it be coming from?

 

Have you tried putting a dye in the oil? That might help pinpoint it.

 

Rear main and/or rear engine plate gasket.

 

I'll have to pick up some of that oil dye tomorrow. Has anyone had a leaking oil pressure sending unit?

It's hard to pinpoint on this truck, because it has a ton of dirt and oil caked all over the place, and a pressure washer with degreaser won't even take the sh** off.

I REALLY hope it isn't the rear main. PITA. I popped out the bellhousing inspection plate and it was clean inside.

 

Wow I duno where to start looking.. Take a look behind the power steering pump.. They all tend to leak from out of the o-ring area. When driving it will blow back all over the oil pan.. Mine did that, it drove me up the ******* wall. Pulled the pan, new gasket, still did it, come to find out thats where it was coming from... But that thing is filthy. I would clean all that **** off of there, to get a better look..

 

What is the hex type bolt/plug above the filter and bypass plate, on the side of the block? Is this just a freeze plug? Or some type of oil gallery plug? It is pretty wet around it.

 

Yes, that's a frost plug for the cooling system. But you're not leaking coolant...

 

Yeah your gonna want dye, and some good degreaser to get all that crap off there.

The point that the oil is covering the front of the pan suggests front seal.

Some Castrol super clean...that will get the oil off. Get the majority of it off with a putty knife than spray it down and pressure wash it. Hit it with some water and Dawn dish liquid to get the last bit off.

Hell, with all the crud on there it could be leaking from the oil soaked muck...and not the engine at all.

 

My vote is the rear main seal and or cover gasket. Seems to be a somewhat common leak on the 99-02s or so. FWIW from GM you can get the cover with gasket and bolts and seal already installed for less than you can get just the seal and the cover gasket and you still have to knock the old seal out and carefully install the new one. I'm lazy and prefer to go the cheap route getting the cover assembly all new ready to go and just bolt it up. Not too likely its the oil pressure sender. If it was the bell housing would be washed clean from the oil and not dirt caked like it is.

 

I had one leak and it ran down just like that. Changed the sender and the leak went away.