What kinda leak is this?

[Jordanlogo]

New to this, but what type of leak is this, and where do y’all think the leak is actually coming from?!

[ArdWrknTrk]

Is it actually coming out of your bellhousing?
If so, rear main seal.

But it is always hard to tell where oil will travel under the hood.
So my best advice is to clean it all off (like spotless and dry) then start the engine for no more than a minute and check again for fresh oil.

We used to use spray on Desenex foot powder as a telltale for weeping.
You can add dye to the oil and a UV flashlight is cheap now that we have LED's. Yellow glasses help.
All this stuff is available at any auto parts or Amazon.

[Gary Lewis]

Jim is probably right, but I've seen several engines leak between the intake manifold and the rear wall of the block and it looked like a rear main seal.  It flows down the back of the block and seems to get between the block/engine plate/and bell housing and then drip out at the bottom.

So do as Jim said and clean things spotlessly, but include the area above the bell housing and at the back of the block.

[ArdWrknTrk]

460's are particularly bad about this, because the oil sender is back there.
Nestled in the 'wave' at the rear of the intake.

[Gary Lewis]

Ditto M-blocks as that's where their sender is.  But, on both Rusty's M-block and Big Blue's 460 it wasn't the sender or its plumbing that was the problem.  It was a shoddy job installing the intake manifold as there was about a 1/16" gap between the manifold and China wall on both of them.  

[ArdWrknTrk]

How do you even miss by that much???

I never use the rubber gaskets anyhow, and just lay a big bead of Ultra Gray or The Right Stuff.

But I did have a leaking sender once, not long after I got this truck.

[Gary Lewis]

I don't use the gaskets either, preferring something like TRS or Ultra Gray.  And whomever did Rusty's and BB's engines did as well, but left a gap in the bead.

Now, we know that was  in BB's case, but Rusty's engine was built here in Okiehoma.  So maybe he was visiting his cousin?

[85lebaront2]

Maybe it was Larry, Moe and Curly?

[ArdWrknTrk]

Hamm Fist???

[Jordanlogo]

Sounds like I’m going to do a lot of cleaning! It’s very minor... like a quarter sized spot on the driveway, but it bugs me that she leaks at all!

Best way to access above the bell housing?

[ArdWrknTrk]

You've just got to get between the firewall and the thermactor crossover with a bottle brush or something.

if it's inside the bell (rear main seal) you're going to have to pull the engine to fix it.

[Gary Lewis]

If the truck's been sitting quite a bit I'd drive it for a while to see if the leak heals itself.  Sometimes seals harden w/o use, and then after use and being washed with new oil seem to soften and re-seal.  I'd sure want to do that before tackling a rear main seal replacement in the truck.  Been there, done that, and don't want to ever again.

[Jordanlogo]

Gary Lewis wrote

If the truck's been sitting quite a bit I'd drive it for a while to see if the leak heals itself.  Sometimes seals harden w/o use, and then after use and being washed with new oil seem to soften and re-seal.  I'd sure want to do that before tackling a rear main seal replacement in the truck.  Been there, done that, and don't want to ever again.

What would I do without you guys?

How many miles are we talking Gary? Also, where exactly did you guys say the other place would be? Behind the engine?

[Gary Lewis]

The other place is at the rear wall of the block where the intake manifold mates with the block.  There's a wall at the front and rear of the vee and between is the valley where the cam and lifters reside.  The intake is supposed to seal the block off, but it doesn't always.  So check at the very back of the intake, right in the middle.

As for miles, 50 or 100 or more.  Not a long time.  But you need new, fresh oil to get to the seal, and it needs to get warm.

[Jordanlogo]

Gary Lewis wrote

The other place is at the rear wall of the block where the intake manifold mates with the block.  There's a wall at the front and rear of the vee and between is the valley where the cam and lifters reside.  The intake is supposed to seal the block off, but it doesn't always.  So check at the very back of the intake, right in the middle.

Copy that! I’m guessing the way to fix that is to take the intake manifold off and put in another gasket? Seems simple enough.

[ArdWrknTrk]

Gary and I both said that we don't use the gaskets.
I mean, you can try, but i long ago gave up on trying to get those things to seal.
High quality RTV  has been the best for me so far.

[Gary Lewis]

Yes - no gasket on the front and rear walls.  Just RTV.  But, the surfaces have to be CLEAN.  I use brake cleaner and scrub to ensure there's no oil or old material.

And, I use long studs in the bolt holes to ensure the intake comes down where it is supposed to be as you don't want to have to move it around much.

Then I install the bolts and run them down finger tight.  Do not torque them.  You want the RTV to touch the intake and adhere but not be squished out.  Let it sit overnight and come back the next day to torque it down.

[ArdWrknTrk]

Any time I do any internal engine work I want things surgically clean.

My own method is to scour with scotch brite, blast with carb or brake kleen and then wipe with acetone and paper towel until I come away with absolutely no residue.

My only real issue is for those who apply a light wipe of silicone around the water ports front and rear.
Tightening hours later has to move the intake gaskets.
But I am wanting to say I have no coolant leaks with no silicone and print-o-seal gaskets. (I have now sealed my fate, and will develop a leak!  )

[Gary Lewis]

Yes, you are right.  Tightening hours later does move things, as witnessed by the bulge of RTV that comes out front and rear.  (Which is why you HAVE TO have things surgically clean so the RTV adheres or it'll just pop out and you'll have a huge leak.)  And that movement will break loose any RTV on the intake-to-head interface as the intake slides down on the head.

I hadn't thought of that, but somehow I've not yet had any leaks.  

I guess in thinking about it maybe I should modify my approach and torque the bolts to something like 1/2 the spec initially and then come back the next day and torque them to spec.  That would minimize the movement.  Or, maybe just go ahead and torque them fully and let the RTV set up w/o pressure?  That way if it didn't adhere at least it might not pop out.  

[FuzzFace2]

On AMC v8's we also throw away the rubber "wall" gaskets for the same reason.
The AMC uses a pan gasket that I bend to fit to the heads before any sealer is used.
After a good cleaning, I do as Jim does, we run a bead of sealer on walls and let it skim over a bit.
Dont forget to clean the intake the same as you did to the wall.

We must use Hi Tack on both side of the pan gasket for the head ports and RTV at the water ports.
By the time you get this done the wall sealer has skimmed over and you can place the pan in place then the manifold and tighten as needed.

I have not had a leak on the wall doing it this way so I think if you let it skim you would also be ok.
Dave ----