I have a relatively fresh 383" that didn't leak a drop of oil. Then I pulled the engine to install a new transmission and (unfortunately) a HV oil pump. It had a STD oil pump in it for 6 months. The HV oil pump was put in due to 0.0030" main bearing clearances. Looking back I only installed the HV pump to make more oil psi at idle just to make me feel better.

So anyways. After I got it all back together I started to notice drips of oil on the ground spaced apart that indicated they were coming from both sides of the engine.

I got the car on a lift and had a look. The back of the engine where the bellhousing bolts to was wet as well as the bellhousing.

It is not coming from the valve covers as they are die cast aluminum ones with a rubber fel pro gasket glued onto them with permatex right stuff. Well I would be very surprised if it was the valve covers. It is not the oil pan or rear main seal. If I wipe things up and then check after a drive, the pan and transmission inspection cover are dry and it is coming down from above.

Since it started after the HV oil pump that now has me thinking that it might be coming from the oil pressure gauge sender area. I have a pipe and nipple and a T there before the gauge because I had a mechanical oil pressure gauge installed.

I guess there or hopefully not the rear china wall seal. It was also done with permatex right stuff.

Any other ideas where to look or how to pinpoint a leak when you can't see much back there?

 

Get a black light bulb and oil dye.
might have to use a small camera or flexible mirror to see behind the engine

 

Good idea. I have a black light flashlight already.

 

GM ENGINE OIL FLUORESCENT TRACER DYE 1 FLUID OZ. P/N 12345795 I’ve used this in the past

 

Check the rear seal on the intake manifold. Long time ago I had a leak that I could not find. Would only occur when the car was driven. Ended up being the China seal on the back of the manifold.

 

It was raining today so I didn't run or drive the car. I was looking around with a flashlight and it is wet around the base of the distributor. It has a gasket and it was new when I put it on.

 

That would be great if it’s just the distributor seal, pretty easy to change out as opposed to the China wall.

Another place back there to check is the oil pressure sender, those can make a mess.

I had to chase a leak back there last summer but it was small and a dab of the grey right stuff RTV took care of it after cleaning the area up. A small mirror was also key in finding the exact spot.

 

Since the pan gasket at the front and rear seals against the crankshaft bearing caps, there's a fine gap between the cap and the block. When you put the pan on, you are supposed to put some sort of silicone at all 4 corners of the pan. I usually use gray silicone in that area.

As for the china wall at both ends of the intake, The Rite Stuff works best.

If the distributor gasket is leaking, you will need to pull the distributor to replace it. Start by making sure #1 cylinder is at TDC, pull the distributor cap off to see exactly where the rotor is pointing then pull the distributor to change the gasket. You probably won't get the distributor back exactly as it came out but it should be close enough to start the engine and reset the timing.

Finding oil leaks on diesels is much easier. Bring the engine up to high idle and plug off the crankcase breather tube with a rag. This will create crankcase pressure and any oil leak can be easily found. On a gas engine, it's a lot more difficult to find small oil leaks.

 

I put some dye in and drove around for a bit. There was some slight indication of distributor seal and valve cover leakage. I couldn't find any trace of a leak at the rear china wall, which is good. Nor any at the oil pressure sender. Valve cover grommets are sweating but not enough to cause the leaks I have.

I am going to clean everything up with some brake cleaner and do it again just to be sure.

**I'm adding that the oil is running from somewhere and dripping off the oil filter and off the starter.

 

I am posting some pictures of the UV dye. I thought it was neat and you might like to see.

As posted before, a tiny bit of oil seepage from the pcv grommet and some by the base of the distributor, but not enough to make the leaks I am seeing. The back of the heads and motor are dry. Behind the distributor is dry, so nothing is running out of the back down the block.

It might actually be coming from the oil pan gasket. The oil filter has some drips coming from the rear and the starter has some drips coming from pan side, and the passenger side bottom of the oil pan has drips. But not a trace at the rear main or onto the inspection cover. So it seems like it would be the sides of the pan which seem weird.

Still slightly mysterious.

 

Based off those pictures, I would guess oil pan gasket especially since you had the pan off recently. Recheck the pan bolts to make sure they're torqued and not over tight.

 

Interestingly enough I got under the car to tighten the pan bolts. As I was peering around I found the dipstick tube not seated. It could be pushed in 1" more. I pushed it in but it was easily moved in and out. I'm using the 1997 vortec truck dipstick. So first I took it out and put a film of rite stuff on it. But it was still really loose.

So I cleaned a threaded hole in the block and made a securement tab and welded it to the tube. I've driven it around today and have it one ramps but haven't checked for leaks, I will do that tomorrow.

 

A update again.

The oil drips down the oil filter.......defective Wix filter from what I could tell. Nothing leaking from the rubber gasket to the block, but oil was found in the seam where the filter can was crimped to the base. I put a new filter on and no leaks from that side.

There was ever so slight indication of oil on the bottom of the starter again. It could just be residue coming off from the top. There was nothing on the side of the oil pan.

I will keep an eye on it to see if it has stopped.

 

Take off the oil filter housing and replace gasket and add avthin seal of black rtv. That happened to my 94 vette whoch zi just finished.