My new engine(s) have been leaking oil out the dust cover and onto my crossover pipe. I just assumed it was the rear seal, and swapped that without a change in the leak. After messing with it for quite a while I have came to the conclusion it is the cam sensor o ring leaking into the bellhousing. I assumed there was pressure in the crankcase from the PCV system, and removed it from the intake. I installed it in my intermediate pipe to help the problem. Well thay didnt work either. Today I decided to pull the sensor (what a PITA), and there was oil above the oring telling me that it was leaking by. I inspected the oring, and could not see any defects in it. I went to a local auto parts store to see if I could find a new thicker oring, but couldn't find one. I flipped the oring over in hopes it would stop the leak as I didnt have another vehicle to drive home. Does anyone know where I could get a thicker oring, or of a fix for it?

 

You sure its not the oil pressure sender. Those are known for leaking like a rear main seal and are close enough to the cam sensor on gen3 motors.

 

It is leaking inside the bellhousing. The oil sender is above the bellhousing. And when I pulled the sensor out, there was oil above the oring suggesting that it was leaking by.

 

We have a truck at the shop that has the cam plug leaking inside the bellhousing. Isnt the cam sensor also above the bellhousing? Sorry all I got are gen4 motors so I have nothing to look at in front of me.

 

The cam sensor mounts right next to the oil press sender above the block. The sensor runs down inside the engine and above the cam. About an inch above the cam, the sensor has an oring. The top of the sensor is just bolted in place, and there is no oring to keep out or in anything. If you take the tranny and flexplate out, you have full view of the cam sensor. That is where i believe the oil is coming from. After a little searching, it appears this has been a problem in the past. I just cant seem to find how anyone is fixing it.

 

Sorry to bump and old thread (not sure why its such a problem to revive an old thread). I think I have a leak similar to your leak. Did you ever find a way to fix it. I haven't torn into it completely, but the flexplate and torque convert is dry when you open up the inspection cover and look in, although you can see some oil/dirt/dirtiness up behind the flexplate, which makes me suspect its not enough oil to be a rear main seal leaking, since if it was the rear main seal I think you would see it more wet with oil behind the flexplate and I think the flexplate and torque converter would have oil on it to. So I think its seeping from whatever on the top of the motor (cam sensor, oil pressure sensor, etc.) and getting inbetween the bellhousing and engine block crack?

I also just pulled the oil pressure sensor off to check and it looks fine, there is no oil in the electrical connector part and no visible wetness around the threads or oil pressure sensor port hole. It usually only leaks a few drops overnight enough to make spots of oil all over the driveway. It likes to collect and drip down from the oil drain plug and filter sometimes. I also suspected the oil cooler (I have a Escalade LQ9 with all the coolers), so I tightened up on the oil cooler bolts that hold on the block thing that connects to the oil filter part of the block.

 

I've replaced a bunch of those cam sensors here at the shop for oil leaks. Just put a new cam sensor in it, comes with new o ring. Worked on every truck I've done it on so far.

And yes if the flex plate is dry, it likely is not the rear main seal leaking.

 

Thanks for the info, I just realized the cam sensor is next to the oil pressure sensor, I think? I just took the oil pressure sensor out and checked it, it looked fine, so I reinstalled it with some thread sealer just in case. I am getting confused now, I know GEN IV's I think have the cam sensors in front, where is the crankshaft sensor then?

 

Above the starter motor

 

I guess that explains why it looks like there is so much oil from my starter motor, but then again its completely covered on the other side too, in places where its higher than the starter.