I have an '01 C5 with LS1. I have a bad oil leak. I have researched all the leak points. Took it to dealer and they said oil pan and front seal. Wanted $1200 for pan gasket and front seal. I put the car on my brother's lift and ran the engine. The leak comes from higher on the engine. He has had experience with this and said either OPS or Cam sensor leak. We pulled the manifold and replaced the o-ring on the cam sensor with one like he has used before on these. The OPS was good with no leak. Put the cam sensor back in with some silicon sealer.

We cranked the engine after the seal dried and with in about 1 minute the oil starts dripping around the passenger side of the back plate above the starter. I could clearly see it when it started around the corner cover up above the starter. It leaks about 1/4 cup of oil on cold crank up.

Here is the mystery. After the engine reaches about 200 to 210 degrees the leak almost stops. Like heat expansion was closing a gap somewhere. I thought the o-ring might be swelling. So I went to the dealer and bought a new sensor with the correct o-ring already on it. I measured the new oring and it was about .015 larger in dia. than the one we had tried. I did not use silicon this time since the factory does not use it when the engine is assembled. They say their is a blue coating on the o-ring that seals it when new.Thought sure this was it.
Cranked the engine and within a minute here came the oil again and only slightly dripped when engine reached 200 degrees.

So what could it be now? Hate to pull the engine to find this. Dealer had said they did not think it was rear seal and that area did not show evidence of oil. Plus I don't think a rear seal would stop just because the engine got hotter. Don't see how a leaking gasket on rear engine plate would do this either.

OK, your turn to talk! Help!

 

Oil sending unit ?

 

Put some dye in the oil and you will find the source of the leak.

 

Dollars to donuts it's the sending unit. Is your oil pressure gauge on the dash acting a little funky?

 

O.p.s.

 

Remember guys in the first paragraph I said the OPS was good . Not a drop of oil on top of block by sending unit and it works perfect. Dye in oil won't tell anything. You can't see where it is coming out. Comes from around corner of back plate not inside. Does not leak from bottom of bell housing.

The only thing I have noticed is that the new cam sensor seats in the block too easily. Seems like it ought to be a snug fit that you have to use a little pressure to seat.

 

OK I bet 2000 donuts! Where's my money? :-)

 

Provided you can see where the leak is coming from. But then you would not need the dye.

 

Without the necessary vacuum to the vent the engine, oil is going to be pushed out wherever it can squeeze through...I would check the PVC system and Replace the PCV valve and hoses if they are original. You can get the pipe with the valve at the dealer for about $125. cheaper online.

 

Yeah I had already eliminated those rotten lines and made up new hoses. The fact that the drip slows when the engine warms up is what is really a mystery. If I could just get my borescope up and around that rear plate I might could see the origin of the leak.

 

Check's in the mail.

 

Hmmmmmmmmmm and you don't even have my address!
Think I've been had. LOL

 

UPDATE:
I pulled the manifold off again today and took the cam sensor out ONE MORE TIME. There was oil on the housing above the o-ring. And puddled on the block. So I believe it was still leaking even though it is a new sensor. I put my old sensor back in with a new o-ring. But this time I wrapped some Teflon tape around the housing to make the o-ring slightly larger by about .020. I also coated it good with RTV sealer. It fit snug this time. I also extended that pesky short HVAC line that keeps coming lose.
Going to let it dry good and crank it up tomorrow. Cross everything you got for me including your fingers. Will let you know the results.