Oil Leak from "rear of engine"

[grabinov]

I have an engine oil leak coming from the rear of the engine. It appears to be coming from the point where the back of the block (where the oil pan ends) mates with the the adapter which then mates to the bell housing of the transmission. It may be coming from the rear of the oil pan gasket.



There also appears to be engine oil leaking from (or at least dripping from) the little cover on the transmission (which I think provides access to the toque converter). It's not trans fluid - which seems odd.



Is the main seal between the block and the adapter, or is the main seal the thing between the adapter and the transmission? As you'll see from my signature, I did have the trans out about 12,000 miles ago for a rebuild.



Any thoughts on where the leak may be coming from?

 

[Wingate]

My 06 with 25,000 miles does that too... its not really an active leak, but more like some minor seepage. It just keeps the area greasy, doesn't even drip...

 

[grabinov]

Do you know if it comes from the main seal or the oil pan gasket?

 

[rbattelle]

It is very common for the rocker box gasket to be rolled at the back, which causes oil to leak slowly down the block.

Mine was doing it, except it was leaking down both sides of the block too. I replaced the seal and it completely stopped the leak. Here's a thread on how to do it.


Considering how inexpensive the gasket (o-ring, really) is, you might start there. You can check it by reaching behind the engine to see if it's wet with oil at the top, just beneath the rocker box.

If that's not it, check the position of your blowby tube. It's possible that it's blowing oil near the back of the block which looks like a leak from the back.

There was also discussion years ago about some oil pan bolts being a little loose. You might consider checking the torque on each one.

Finally, if none of that is the problem, it could be seepage from the rear main seal. This could be indicative of a leaky rear main, or it could simply be minor seepage from that seal. All rotating seals will seep a little by design (seal life is inversely proportional to leak rate). If the seepage isn't enough to stain the driveway, and the oil level remains constant within a quart between oil changes, I wouldn't worry about it.

Ryan

 

[grabinov]

Thanks for the insight Ryan. I took a look at your old post re: the rocker box gasket. Mine is definitely leaking from either the rear of the oil pan or the seal between the block and the transmission adapter - I have no oil at all on the rear of the block or head. At least that's a good thing!

The leak/seep is just enough to leave a little spot on my driveway (bad) but is nowhere near a quart per oil change (good). In fact I don't think it leaks at all when the truck is cold in the driveway for days at a time - it only leaks when the oil is warm.

I did tighten the bolts at the rear of the oil pan - the old "just tight enough" method. They were looser by about an eighth of a turn than those at the sides and front of the pan, which did not move at all when turned "gently". I'm hoping that the leaks was from the pan, and that I may have fixed it...

If that doesn't work I am gonna be looking for a post on tightening the trans to adapter to block bolts...

Greg

 

[macdaddy]

Try This

Greg



If there is a little drip gathering on the back oil pan bolts (10mm). Remove the bolts using a generous amount of break cleaner, clean the threaded hole and bolt well.



Now use a "Good Quality" high temp silicone sealant and dope them up real well and reinstall them to factory torque specs with the engine cold. Allow the sealant to cure for 24 hours by not driving truck.



My 05 was doing this and it stoped the leak dead in its tracks. Like you I thought it was a main seal.



Mac

 

[grabinov]

Will do Mac. Sounds like a plan for the weekend. So it's probably oil leaking form the bolt holes then...

Thanks,

Greg

 

[macdaddy]

Greg



My 99 had the same problem... ...



Bob4x4 hooked me up with this fix. It is leaking past the inner part of the pan gasket and coming out the bolt hole... .



I thought of you servicing my trans yesterday when I was noticing how the leaking oil had stoped.



Mac