95.5 Tacoma 3.4 Mystery oil leak

Hello all me again.
So I’m December I had cracked my block and replaced the engine on this thing.
Long story short did my clutch and a boat load of seals before putting it back in just cause “while you’re there” syndrome. I had a local Toyota guy do the work as I was out of town for work.

List of seals done:
Rear main seal, Victor Reinz brand
Toyota OEM injector seals
OEM Spark plug gaskets
OEM Valve cover gaskets
ORM Oil pant (with Toyota black RTV)
OEM Call shaft half moons and rubber full circles
Only things we didn’t reseal was the head gasket and pumps.

Sorry I’m advance lots of details below:

to the matter at hand, I have had an oil leak for about 3 months, I and 3 of my buddies couldn’t figure it out. Even the tech who did all this work couldn’t find it.
Sometimes it drips 1-2 drops other times is a small 2-3” puddle. Guess it depends on how temperamental the truck is feeling. I changed the oil a week ago with Mobil 1 5W30 full synth as I always do with filter. The oil was over filled .. the drips are coming from the inspection plate mounted on the bottom of the bell housing. It’s a 5 speed and my concern was RMS but we did that?..
The oil is leaking from the inspection plate or maybe the back of the oil pan as those are the only two areas with fresh oil near them. I pulled the plate and did not have any oil inside the walls of the bell housing or the fly wheel. Oil was only on the inspection plate and dripping onto the steering rack. It’s definitely engine oil based on smell and look. If anyone has had a similar issue please chyme in, getting a little desperate and about ready to have a shop go top down on it to check it out but hoping to avoid throwing money away chasing it to find out it’s a silly thing.
Thank you in advance hope that’s enough info to start with.

 

Below I attached other pictures, close up of the fly wheel (only have so many photos) will need to take more.
And I removed the starter cause it looked wet around that area thought it might give me a better view of something else leaking? Seems oily around there.

 

I chased leaks on mine since it was 6 years old, finally got em all for now.

Seems like most of the leaks end up back there, possibly due to air flow.

The worst is the cam plugs, I put RTV on them even though FSM does not require it because those plugs have a very thin layer of rubber on them. Sounds like you replaced them - rubber circle things?

Anyhow other culprits are oil cooler, oil filler cap seal and the dipstick o-ring. Might as well replace those since they cost next to nothing and are trivial to replace (oil cooler coolant lines are a bit frustrating - long reach pliers help).
You wouldn't think the oil filler cap would be a source but that one fooled me for a long time - it was hard as a rock after 15 years.

 

yes the “rubber things” haha I’ll double check them cause there definitely isn’t RTV on those.
Thanks for the reply dude

 

I've just referred to them as the cam dummy seals - not sure what they're actually called. I did add some extra FIPG to these areas on both sides as well as resealing the aluminum half moons. This extra FIPG is recommended from what I read.

A flexible mirror should help you put eyes on the back sides of those seals. Mine has helped me verify no leaks after the valve cover job.

*EDIT* I also went ahead and replaced the seal under the oil fill cap itself. When tightening it down with the new seal I could feel it seat more securely.

 

Sometimes you have to clean the oil off the best you can, and then add dye.
Let it leak again and trace it back to where it starts.

 

I do have a mirror and have looked at the back of the seals. The whole back area was slightly wet. Could not see any new oil coming from it however I’m going to take the advice below as well. Gonna wipe it as clean as possible top to bottom, dye it and cross my fingers it’ll pin point the issue. Hoping it’s something as silly as the oil cap seal leaking and letting oil at weird times. Will edit and update in the next 48 hours with any progress if it’s found thank you guys do appreciate this insight. Also thanks for the photo for future reference will retain that if these need to get done again.

 

I am wondering if your rear main seal was defective. If you cannot identify a leak coming before the flywheel, the rear main seal might be the culprit. I'v had to deal with a fair share of defective parts and its always a pain to deal with.

 

Ok so quick update. sorry I didn’t get back to anyone if they were curious about the issue here, one of my brakes seized up had to deal with that.

Anyways, I checked m my o ring connection on the dipstick no leaking not even a sweat.
Oil filler cap is good has some residual oil on it go a seal and replaced it anyways.
I wiped off the back of the engine best I could, I did notice the rubber cam seal on the real (full circle style seal) was a little wet around the edges but didn’t get worse after a good 15-20 min drive.
The rear of the oil pan and about1/4 passenger side oil pan are wet consistently.
I’m leaning towards rear main seal was defective as stated above by another Gent or oil pan is leaking at the rear most area that is covered by the inspection plate meeting the bell housing. tomorrow I’ll be picking up dye on my way to work and doing that, hopefully that gets it narrowed down to a 90% certainty

 

Ok another update sorry been a whack week with work.
I died the oil and drove it up to the car wash to ungunk my suspension n such.
About 35 km of driving. Hopped under the truck, popped the viewing plate of the bell housing and it appears all the oil leaking down from it and onto the plate is coming from the rear of the oil pan. No bright green oil in the bell housing at all except for the oil pan. I’m going to inspect further when we aren’t getting rained out but I’m feeling a lot better about this being a botched oil pan seal job !

 

I sure hope it is just the pan and not that rear main seal after all the money and time you put into it...

 

here’s hoping. I might leave a small bead of black RTV along where it’s leaking and see if that might help. Guy on one thread was chasing my issue and thankfully it was his pan in the same place. Worse case a weekend with the diff out will be in my future and pray that is the solution. Will update again once I get there so if anyone down the road has this problem they can reference this.

 

Well sad to say it was the rear main.
Shop I have it at right now is a friends and let’s just say they found some sad things.
The bolts for the retaining seal around the rear main weren’t sealed so oil was also leaking through all the holes the bolts thread into and the shop I had install my clutch and rear main also destroyed the threads on the bolts holding in my flywheel as well as all my transmission mounting bolts to the crossmember were snapped. So this shop I had do the work broke things left and right, neglected to tell me and didn’t even try to fix it.
Edit: thankfully where the oil was leaking from didn’t cause the clutch to get soaked and the starter motor was only mildly wet with some oil being flung around. Even tho form the inspection plate everything seemed fine and no visible oil along the walls. So all in all hurt wallet but happy ending. Truck should be 100% now as that has been the only mechanical issue I’ve had the last 5-6 months

To summarize it is the rear main seal and Vet your shops before you trust them with your old trucks you dump to much money into.
Thankfully the oil pan is tip top and that is in fact sealed tight. They did one thing right it least

 

I had a feeling it was the rear main seal. Usually, a leak showing from the rear of the oil pan is an indication that the rear main seal is bad. It sucks that you went through all the trouble but glad you got to the bottom of it!

 

thanks brother just happy she’ll be set mechanically now I can worry about painting it and fixing the northern rust lol