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So a week back I drained all my old oil, pulled the oil pan, and installed a new Fel-Pro gasket. The old one was also a Fel-Pro, but was cracked at the back - which led to a slight oil leak down the front of the transmission (or so I thought).

I followed the instructions to a T and torqued all the bolts down to the proper specifications... and now I have an oil leak at the front near my crankshaft pulley from the rounded part of the gasket AND I still have that slight leak at the back where the engine meets the transmission. I cannot figure out for the life of me why either is leaking (the front shouldn't be leaking because it wasn't before, and the back I just can't see where the oil is coming from, I just know that it's running down the plate)

Any ideas on what I should do about this? I'd really rather not be leaking any oil at all since the Unisteer rack goes right under the pan. Don't want it to get all nasty and screwed up, and I'm really trying to do this right. I'm just getting frustrated because I can't get this leak to stop!

I've got a 289 engine and am using Valvoline VR1 Conventional 10W-30 Oil.
 

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I have been fighting the worst transmission pan leak for years. I think I might have stopped it, but I haven't been out to the garage much this winter. If it is still going, it is a slower leak now.

Did you inspect the mounting surface on the engine block? My transmission pan mounting surface had a few nicks that could have made it quite easy for a leak to find its way out. I only noticed these while getting underneath with a good light and searching for nicks and scratches. Did you check your oil pan to see if the lip is straight?

Also...as I hear so often...did you clean the crap out of the mating surfaces and make sure they were dry?
 

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Yes, the mating surfaces were good - scraped with a putty knife, given a going over with a wire brush, and wiped with a damp rag then a clean rag. Bout as clean as it's going to get! :)

How would I find these nicks and scratches? It might be that, but it almost looks like the oil is coming from higher up than the oil pan sometimes. But then when I run my hand all over the back of the engine to check for leaks, I come up with a little dampness but no real leaks... :loco: Mysterious.

Here is what the offending leak looks like:


(That picture is taken before I scraped and cleaned the entire surface)

Right now it's coming down from the dead center, where I circled, but you can see that in the past it has forked down on either side. I've caught both of those things occurring, and it's always enough to put a half-dollar-sized puddle of oil on the floor.
 

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And this is the part where I really wish someone would teach me to take apart my engine and put it back together.

But alas, I have no such luck, so I must ask the question... what rear main seal? Where? How would I check? What tools do I need?
 

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I'm pretty new to taking engines apart also. The rear main seal is at the back of the engine, where it meets the transmission. It keeps the oil in the crankcase from spilling out. It seems like the easiest way to replace it is to remove the engine but I read about removing the main bearings from underneath being another way.

If you remove it from underneath, you are messing with the crankshaft. You must torque it back to specs. Leaks are funny. Check all over to make sure the oil is not dripping down from somewhere else (somewhere higher up).

Someone will come to the rescue eventually, but I wonder if dropping the transmission will allow enough room to replace the seal.
 

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Could be rear main seal. rear cam plug, or if you are lucky the rear of the intake manifold or valve cover gaskets if you are really lucky. How is your crank case ventilation. Do you have a PCV valve/breather setup? I had a leak last year that i tore the entire engine out of the car to fix without success. Replumbed my PCV, hooked up a ported vacuum breather cap and my leaks went away. Which gasket did you buy? Was it the silicone one with the metal insert to prevent overtorquing? Is your oil pan bent maybe? Just a few ideas...

Jafo
 

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I bet it is the rear main seal. I had the exact same leak and after changing the oil pan gasket it still leaked. I took it back apart and changed the rear main seal and that fixed it..
The rear main seal can be a pain in the butt!! You first drop the oil pan again, then you have to drop the rear main cap. Part of the rear main seal is in that cap. The other half is in the engine block. You have to force the block side of the seal around the crank and slide it out of the block. The problem with mine was when I put the seal in the first time (building the engine) I lined the seal up wrong. You dont want the edges to meet at the same place your cap meets the block. You want to slide the seal up in to the block a little and let them come together up in the block. It is so hard to describe in words but here is a picture of the seal offset like im talking about

I put a little silicone on each end of the seal to make sure nothing slipped thru.
The hard part of this is getting the seal out of the block side of engine. I have done it before where they just slide right out. But this last time I had to drive it out at first then it slid the rest of the way out. TIP ( loosen all the main caps and let the crank drop a little. Usually the seal will slide right out after that.)
Putting it back together is not bad at all. Just be sure to offset the ends like the pic and dont scar up the seal. Make sure you have it in right to. It is possible to put it in backwards... Read the directions that come with the seal!
 

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Leaks can be hard to stop sometimes...I completely rebuilt my engine last spring, made sure every single gasket was installed perfect (some with sealant, some not), paid extra careful attention to the split rear main area, etc., etc.....and I still have a leak coming from somewhere.......not a major one, but one that just torques me off.....However in my case, it will stay that way until the engine comes out the next time (unless the leak gets worse).

Actually a couple of leaks, but I know in one instance it is my cheap, old school, chrome oil pan (I should have recalled how those leaked back in the day)....:)
Tom
 

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Yes, the mating surfaces were good - scraped with a putty knife, given a going over with a wire brush, and wiped with a damp rag then a clean rag. Bout as clean as it's going to get! :)

How would I find these nicks and scratches? It might be that, but it almost looks like the oil is coming from higher up than the oil pan sometimes. But then when I run my hand all over the back of the engine to check for leaks, I come up with a little dampness but no real leaks... :loco: Mysterious.

Here is what the offending leak looks like:


(That picture is taken before I scraped and cleaned the entire surface)

Right now it's coming down from the dead center, where I circled, but you can see that in the past it has forked down on either side. I've caught both of those things occurring, and it's always enough to put a half-dollar-sized puddle of oil on the floor.
Hi,
Are you running a PCV system? If so, is it working as designed?
The reason I ask, a PCV systems not only reduce crankcase emissions, but, pressures, as well. This pressure tends to push oil and oily seepage out every nook and cranny opening. Seepage has been known to be slowed or even stopped by improving the PCV system. Not to mention, and through more extreme measures, there have been parasitic HP gains, as well.
Just another consideration.
 

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Discussion Starter #11
Bear with me, because I just had to look up what a PCV system is (with a small degree of success) and the best I could figure out is that it's a hose that runs from the passenger valve covers to the carb? If so, then yes, I do have one, and no, I have no idea if it's working as intended :)

I put in the Felpro one-piece gasket with the metal inserts to prevent overtorquing, yes. Dabs of sealant on the corners and nowhere else as recommended, torqued to specifications.

How would I check for leaks on the seals higher up on the engine? I mean, I've stuck my hand back there but I have no idea what I'm feeling... is there a better way to do this?

The problem is that I have to fix this problem with the car on jackstands without removing the engine or transmission, as I have the means to do neither. As a person new to engines, I think I know better than to start removing stuff and screwing with it if it already works. With my luck, I'd never be able to get my transmission and engine right ever again and the car would run like s***! :)
 

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you could do what i did break all the pushrods and then take the engine completely apart in the car and put it back together. now its the trans that went out....... fail
 

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Checking the pvc is as simple as pulling the valve out of the cover while its running and seeing if it will hold a piece of paper to it. Yes it is working. No it is plugged and pvc valve needs replacing.

As for the leak, Check the rear area of the eng by using a mirror and a light to see around the backside of the intake and block.

From you pic posted, it most likely is the rear main seal.
Now that your a pro at removing the oil pan, the rest is simple.

Pull the pan and remove the rear main cap.
If it has the 2 piece rubber seal its simple, if it has the rope type that is alittle more work involved to replace.
Rope seals require a tool to remove and replace, It can be purchased from any good parts store with instructions on how to use.

2 piece rubber seals are simple, after cap is removed from the block take a small punch and lightly tap one end of the seal that remains in the blocks groove. This will push the seal around the crank and protude slighltly on the otherside. Clamp a pair of visegrips on it and tap them with a small hammer while following the crank around. Do not try and pull straight down as there is a metal band inside the seal and it will bind if pulling straight out.

Reinstalling, First I use pipe cleaners soaked with parts cleaner pushed around the groove to clean it, this will help in installing the upper seal half.
Lightly coat the seal half with oil and slide it back in the groove(make sure its facing correctly) and off set the end 1/4 in.
Clean the cap groove and install the lower half with the end matching the offset of the upper.
Apply a SMALL dab of sealent on the ends and replace the cap and tork the bolts.
Replace the pan.
 

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Ok, I can definitely check my PVC then, it sounds easy enough. If it won't hold the paper to it, what does that mean? (Well, obviously, not working, but how would I go about fixing it?)

What kind of sealant is recommended for the seals? I think I saw something about RTV in another post about rear main seals when I searched earlier. Furthermore, where can I get a good new seal? Not sure if they're Mustang-specific or anything.

The offset on the seals is just to keep the edges of them from being in line with the cap, correct? So the exact offset doesn't matter, as long as it's somewhere around a quarter of an inch.

Are the torque specifications for the rear main cap listed in the '66 Shop Manual? I don't have it on me right now, so I can't check. I just like to know how to put everything back together BEFORE I take it apart (learned that lesson the hard way! :pirate:)

Thanks for all the help guys. I'll find a mirror and check the back of my entire engine too this weekend on the offchance that it's a different seal... which I'm really hoping it's not. Because I don't know how to fix any other seals either! :p
 

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The PCV should be creating suction, which you can feel if you put your finger over the valve itself unplugged from the valve cover. To replace the PCV, you'd pick up a new valve at the auto parts store for maybe $5, but see if there is a part number on the old one to make sure you get the right size/shape. The rear main bearing seal can be had at rock auto for example for $5-$10 (made of rubber, other styles are more money.)

I recently attempted this repair myself, but honestly the upper half of the seal was a bear, wasn't installed offset, and loosening the main caps didn't lower the crankshaft, so I couldn't even drive it out. Replacing just the bottom half of the seal won't work well, as I found out. :) Ultra Black is a popular RTV. The main cap torque is 70lbs, and the sequence I found was 3,4,5,2,1, in three steps as needed. HTH
 

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If it is the rope seal, you don't need any special tools other than a 1" long #6 sheet metal screw, screwdriver and vise grips. You screw the screw up into the rope seal almost all the way and use the vise grips to pull the rope out while pushing on the other side with a screwdriver.
Remove the "spike" in the main cap (using a punch)to hold the rope seal and replace with regular seal.
Also, if the flywheel/flexplate bolts have ever been removed and not replaced using RTV on the threads it will also cause a minor leak.
 

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Discussion Starter #17
I wouldn't think i still have a rope seal, as the engine was supposedly rebuilt 7 or 8000 miles ago. But if I do, then I'll know what to do about it, thanks for the info :)

I'll check the flexplate/flywheel bolts too if I can - how many are there total? I can see the two on the bottom in my pictures but don't have pics of anything further up. Don't think it's them because there's not any oil leaking from them that I can see, but might as well check since it looks like I've gotta screw with it anyways (sigh)

I swear, this rack and pinion is never going in.
 

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Discussion Starter #18
Also: when purchasing a new rear main seal, do I just want the Felpro 2-piece rubber one, or the Felpro high-performance 2-piece one?

Rubber vs fluoroelastomer
 

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I feel your pain. I just replaced my front and rear mains (off set this time for sure) and a $20 metal/rubber one piece pan gasket. I'm still getting a drip leak down the tranny plate just like yours. I fixed a tiny leak at the rear of the intake and I've checked all over the back end and I STILL can't figure out where it's coming from. I keep telling myself there's no way it could still be the rear main after I had just replaced it with the motor out, but I guess I'll end up doing it again if it persists. I will test my PCV today to make sure that's not it. BOY would that be a nice easy fix.

Good luck!
 

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The offset isnt a particular amount. I do mine at around 3/8". When you get all the main caps loose the crank will not just fall down. I put a socket and strong arm on the harmonic balancer bolt and started to turn the crank a little and it dropped for me. Its a lot easier if you pull all the spark plugs. I didnt though cause its a pain!
U dont want to take the main caps off. Just loosen them enough for the crank to fall 1/8 to 1/4".

As far as the 2 types of seals, not sure why you would need the high performance one. I would just get the rubber one...
 
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