(EDITING POST. NEW INFO.... now thinking leak may be rear main seal? Pics now attached. Whadda ya think?)

Engine rebuild seems to have gotten all the leaks but one. Oil leak at rear edge of oil pan. Thin continuous stream, not pouring out but not drip drip drip either. Certainly enough to not want to drive the car.

Pan has a pretty good sized dent/crease at its lowest point so took a good whack from a curb or speedbump at some point. (May also explain why the oil cooler was held on by zip ties). The interface between pan and engine did not appear to be warped, however I was NOT looking for a warp so could very well be the cause of the issue. A fairly deep search showed replacement pans are be hard to find. So....

- Anyone know of a source of replacement 12A oil pans? Willing to pay if more likely to result in a fix that holds.
- How to straighten an oil pan warp? Worth even trying? Careful use of hammer on the flattest piece of plywood I can find is what I am guessing.
- Use a Banzai Racing pan brace when reinstalling? The ex-architect / engineer in me says it makes sense, and the idea of using studs versus the stock bolts appeals as I will be crawling under the car which is not my favorite thing in the world.

Not even going to ask about gaskets and sealants. My Lord that question leads to a deep rabbit hole.

 

Is this while your car is level it's pouring out? I love to ask the dumb questions

1. Do you have RTV or a gasket between pan and block?
2. Have you gently tightened all of the bolts to ensure it is actually snug? We have this problem all the time and usually fix by snugging it up. Carefully of course, or you'll torque the heads off of the bolts.

 

Yes, car is off the ramps and on level ground. Rate of leak?... Imagine a kitchen faucet adjust to where the drips just turn into a thin steady stream.
Pan was installed with a Gasket from Atkins Rotary. Bead of Right Stuff both sides of the gasket. Tightened to 8 foot pounds.
Going to crawl under this morning and check the torque. The pan was installed before the engine was craned back in so maybe something moved as we banged it around trying to mate to the bell housing. Did I tell you how much I hate crawling under the car. Working in the street, kinda busy with traffic, in an earthquake zone.

 

Anything above the rear of the oil pan that may be leaking? Ran the engine again, and pretty sure I see fresh oil an inch or two above the oil pan gasket joint. Oil is dripping dead center rear of the pan, right on its edge. However I see oil starting around two inches above the pan, both sides of the joint between bell housing and rear iron... just forward of the silver bolt that holds the bell housing to the rear iron.

Worst case scenario is oil is leaking from the rear main seal and dribbling down to the bottom of the bell housing and escaping at the lower edge of the housing.

- Anything else near or above this area that could be leaking oil? Cant see a darned thing due to intake, exhaust and heat shields.
- Would the upper inspection panel on top of the rear iron that allows me to see the back of the flywheel be any use? If I pulled that would I have any clues eg oil on the flywheel?

And just in case the info is useful, front of the car is jacked up around 9 inches. Leaks when engine running but not when stopped or cranked. Checked torque of pan at 104 inch pounds. Oil ends up at rear of oil pan, thin steady stream. Main rear seal was replaced during rebuild.

And to look on the bright side, car started again with the help of ether spray and idled nicely once warmed up with almost no smoke.

 

To me if its leaking when engine is running but not when it's stopped - it's not just the oil pan (IMO). This suggests its related to the pressure side of the system vs just the pan gasket. the oil when running should be slightly lower in the pan then when stopped and sat for a bit.

If you pull the inspection plate, you might be able to see something but I know access is ****. Only things I can think of are a leak at a tention bolt, or rear main seal but there's not a ton in there.

Do you have indicated oil pressure when running?

 

Thanks for the ideas. I do have pressure. 30psi when cranking over, which I did note as was checking for oil pressure before engaging fuel pump. I believe it was running 60psi at 2000 rpm when I was warming the engine but will check next time I start.

Am going to clean off the leaking area and run some UV dye in the oil tomorrow and narrow down the source. See if I can prove to myself this is more than pan and requires pulling engine again.

 

Take the starter out and see if there is any oil inside the trans area. Like said, also take the passenger side inspection plate off.

 

There is also usually the big rubber grommet on the bottom of the bell housing as well IIRC - been a minute since I've messed with a tranny...

 

I believe only the 1981 onward have that plug.

 

I will take a look for the plug, thats an easy thing to pull and see if oil runs out of the hole or if I can see anything inside. If not, and oil dye indicates oil is coming from the bell housing, I will remove the starter motor and see what I can see. The car is an '81... but its an odd mix as has FB style fenders but an SA style dash / radio.

 

Yup. Oil coming from inside of bell housing. Somewhat relieved as main seal seems a more predictable fix than a leaking oil pan. Then again... we replaced the main seal in the rebuild. The learning continues.

 

Wow this is a mystery , really have me thinking on this. I would be very suprised that if would be the rear main seal as you said a new one was installed . Just curious if a new o-ring was installed on the rear main stationary gear ? Even if it wasn't I wouldn't expect a ton of oil to escape past , but your oil pressure numbers sound right . Would be a super rarity but the rear housing / iron had a hairline crack somewhere ? I have never seen that on a nitrided 12A iron yet , but man oh man , where could if come from ???

 

Redline. Tell me more about the O ring. There was one leftover O ring from the Atkins kit. It was not covered in the Atkins rebuild video so I ignored it as the kit included several pieces that only were used if taking the carb apart etc so assumed it was not required in the rebuild of the engine itself. By any chance would this O ring be around 4 inches diameter, maybe 1/8 inch thick? If so... you may have the answer to the puzzle. The tranny is coated on old black oil so maybe the O ring was failing before the rebuild.

 

Also make sure it's not a tension bolt with a bad seal.

 

Did the o ring you mention look like this?

If so it goes in this little groove , and unfortunately may be your issue.

 

I think the stationary gear can be removed carefully and the oring replaced without pulling the engine apart. Saw that in some other post on here not too long ago. Still have to drop the tranny tho. Bummer.

 

Much appreciate the info guys. Checked my bag of left over parts from the Atkins kit and does look like that we failed to replace that ring. Kind of happy to find out I missed something definitive rather than being stuck with a mystery leak. An auto club with lift access just opened up a couple of blocks from us so will book some lift time, remove the transmission and replace the O ring... but first some digging to make sure its possible and that I have all my parts lined up.

And dumb question. With a vehicle up on a lift is the only way to support the rear of the engine when the tranny is removed to use a hoist beam across the top of the engine. One more single use part I need to buy!

 

Yep , that is exactly what I was thinking about . If thar o-ring is missing altogether ( during assembly ) the gear will very easily slide into position in the rear iron. And subsequently leak like a sieve ! With a new o-ring , it will be tight on install into the rear iron , and likely will only press in as you tighten the 6 bolts up .
Glad you have identified the probable cause , but a shame that it requires so much work to rectify.

 

I win Idiot of the Year.

Cause of the oil leak was indeed the main seal on the rear fixed gear. Or to be more exact.... it wasn’t the main seal. Because it wasn’t there! Big empty seal shaped space where it was supposed to be.

We rebuilt the engine starting at the rear iron and worked out way forward learning as we go. I guess the rear fixed gear and seal was the first thing we did and we knew absolutely nothing at that point!

Thanks for all the help with lift pad points, chaining the flywheel, using a crowfoot to pull the rear gear... would still be scratching our heads without your help.

Tomorrow we put rear gear, tranny and shaft back in again. Cant believe some of you do this without a lift. Hard men indeed.