Have been fighting a determined oil leak for a long time, and thought I finally had it, but there seems to be a tiny amount still coming from somewhere. I have access to a full lift, lots of light, and time, so I've looked all over the engine. There's no oil coming from the intake (had that off and painted / reinstalled it) on either end, none from the oil pan gasket (new one piece and bone dry everywhere), none from the valve covers, none from the oil pressure sender, ditto the fuel pump area and rod bolt, so I'm at a loss as to where it is coming from...except that it might be the filter on the back edge, could try tightening a little but I doubt it is that, or it is the rear main seal. I just did this job about a month ago...when it was leaking before though there was oil all over the front and back of the inspection cover, and it could be seen coming from the lip around the pan and the crank looked wet, etc. Now all I see is a tiny, tiny bit on the seam beside the filter between the block and bellhousing, none on the flywheel at all or outside of cover, just some on the mating surface for the cover, crank looks dry, and not enough oil comes out even for it to drip after running for 20 minutes or more.

I cleaned like a mad man, used high temp RTV in the correct area as the GM manual says to, installed the seal in the right direction (lip to front) with an off-set of 3/8", etc., lubed the seals a little with oil on the crank side as recommended, even waited a couple of days before I put oil back in the engine.

I'm wondering if I didn't torque the cap bolts enough...first time I did the job, and the torque chart from the GM manual can be unclear...says 75lbs, but outer bolts on engines with 4 bolt caps 65lbs. I split the difference and went with 70. Rechecked a couple of times before the pan went back on. Did I go wrong here?

Here's an older pic with some high talent drawing to show you what I mean, green shows where I see a bit of oil (not enough to drip but it's there, and only driver's side):

 

Sure it's motor oil and not gear oil?
Smell it - gear oil has its own odor.

 

Wash everything with alcohol- spray bottle works well- let it dry, then dust it with baby powder. Little messy, but any oil will track in the powder like a big red neon arrow to the source.

 

More then likely its the rear seal, was there any type of groove in the crank? There are different types of seals that felpro makes, the torque isn't the problem.

 

It´s leaking along that green line. If it was a rear main it most likely be dripping down the rear of the pan. Thats odd that it would be coming from between the block and trans.

Also you figured the GM torque specs were not clear so you made up your own.

 

Looked very carefully for a groove or any imperfections, did not see any.

No oil at all down the back of the pan, dry as a bone, can see it clearly on the lift. This is where it leaked before, and no longer does.

I know there's the cam galley plug back in there that could in theory show itself through the seam at this location.

Will have another look and see if I can determine if it is gear oil, but I'm fairly certain it isn't.

I've read so many different torque specs for the cap, 65, 70, 75, 80, that I chose 70. Seemed like a safe choice.

 

I seriously doubt torque is the issue.
cap is down.
them seals are tricky to get right.
i am not saying you did not get it right.
just that the torque is not the issue.

 

When you put the seal in, did you offset the ends so that the join isn't level with your rear main cap?

 

Thanks cal, makes me feel better knowing that part isn't the issue.

 

Bagmup, yes 3/8" offset.

 

Maybe the back of the valve cover or maybe the distributor gasket.
Oil sending unit. Rear of intake.
Where you are showing the leak it dosen´t look like a rear main or a pan.

 

Sometimes it's tough to nail down an oil leak, especially when the oil is clean and the block has good paint on it still. The oil becomes near invisible.

 

I'll have another look at all areas tonight, though they all appear very dry. I am certain it isn't the intake or the sender.

The reason I go to rear seal in my head is because of course it is the only one I can't see, other than the cam galley, I will have another look. Car has come a long way since April though, happy otherwise.

 

Should note the reason I'm so confident about the intake is that I just had that off and reinstalled it...so the areas around it are very clean...makes it really easy to spot anything.

 

That's a great idea, it really shows where an oil leak begins, but it's easier to use the foot powder that comes in a spray can. You can spray it right where you want it, it's nice and bright white, and sticks real good, but easy to clean off.

Scott

 

This will seem weird and likely won't apply, but it seems you've eliminated the usual suspects, so I offer this for consideration:

In Ford's F-150's, (1986-1996), with the 5 speed manual transmissions (Mazda-made, believe it or not), there is a rubber plug or dohickey up on the top side of the trans. It degrades, and allows a small leak to run down the side of the trans, about mid-way back (I realize your leak is near the front of the trans, but bear with me).

It was slow, and required a top up of ATF only every 6 months (yup, those Mazda manual gearboxes take ATF). But those who failed to add oil eventually had to buy/rebuild a transmission. It only leaked when in use, so the "spotting" on the driveway seemed insignificant.

I don't know the answer to this, but is the ANY chance it's escaping from the top of the trans? Like from around the shifter/linkages, or from a cracked casting?

Just tryin' to help.

 

when you changed the rear main seal did you put a little sealant on the rear of the cap mating surface? Another thing that was causing my oil leak was the oil sender itself.Not the oil port but out of the sender itself!

 

Another possibility (oh, I hope this isn't your problem...) is that you have developed a leak at one of the 3 pipe plugs on the back face of the block (oil gallery hole block-off plugs). They are sealed at the factory--but the car is 40 years old. To see if that is the problem you will have to remove the lower inspection cover, put some flourescent dye check in the oil, use the little penlight black-light you get in the dye check kit, and try to peek up into the crack between the bell housing and the engine block.

I had one leak on me AFTER I made a transmission change. Then, I had to disconnect the tranny again to seal it back up.

 

Ok I had another good look today. Ran the car for a bit to try to get some oil to show up. The back of the intake and sending unit are very, very clean and dry - so those are out. Valve covers appear the same. Does not smell like gear oil - not stinky.

Snapped a couple of pics. Same thing as before - pan and flywheel totally dry, just shows itself at the seam between the block and bellhousing and the driver's side corner and runs down from there. Was able to stick a finger up around the crank itself and it is very dry. The little "ledge" at the back of the block up inside is a dirty place, and it might be coming from there, 7T1. Note the blackish area to the left of my green line inside the bellhousing is just ancient grime, not oil.



One to show how dry everything around the pan lip and crank really is - no traces of oil at all (it leaked badly here before I replaced the rear main and pan gasket):



Only place on the inspection cover where oil is present - driver's side edge against bellhousing as shown in first pic:

 

Any chance it's residual oil from between the block and bellhousing?