rear main seal advice...

[defiance]

So I had my engine on the test stand, and my to-do list before starting it had about 5 items left.  I was shooting for Friday..............

Now it's back on the work stand, upside down, oil pan/girdle off looking for a rear seal leak.

Basically, as soon as I started priming, oil started dripping out of the transmission.  Pulled off the tranny and the oil was coming from the bottom side of the crank seal (I think anyway - the flow was coming out from under the flexplate flange). 
So I now have the rear main seal pulled off and I don't really get why it's leaking.  Maybe I don't know what I'm looking for, but the seal really looks fine.  I'm using the billet cap from 440source (which I believe is made by mancini), and the 2-piece rubber seal.  The crank has cross-hatching in it where the seal seats, but I assume that's intentional and normal.  This engine has turned a whole 5-6 revolutions since machining, mostly just for clearance testing- so I KNOW I haven't worn down the seal.

Any advice for what I should try to get it sealing properly?

[General_01]

This is just a question. Nothing meant by it, but are you sure the seal is on the right way. Just stating obvious things to check. It has been forever since I put a rear seal in my engine. Probably about 10 years, so I am not an expert. But I remember my cousin telling me to make sure I put it the right way or it won't seal.

[RD]

did you silicone the upper and lower seal in its groove?

[tecmopar]

There is no pressure on the seal so it should never leak when just priming the motor, it gets its little bit of lube just from splash. I would remove the flex plate and check the rear cam plug and the other 2 plugs back there to see if one of them is leaking, good luck.

[defiance]

No, it's definitely the rear main seal.  The flexplate is already removed, and it's very clearly leakin from underneath the flange. 
I didn't install the old seal originally, but it had silicone on the joint between the two peices, and around the outside edges.  I don't know that it was *right*, but it was there... 

What can be done wrong to make it not seal?  Direction?  If so, what direction is correct?

[BrianShaughnessy]

I have a best machine block waiting to go onto my new short block.

The destructions say you'll likely need to have the mating surface planed about .010 if you've had a align bore / hone job.

This is a tech bit off the 440source site itself...   

As a tech tip, if you are having problems with rear main seal leaks, have your machine shop surface a small amount of material (approx. .010") off the bottom of the rear seal cap using their Rod/Main cap cutter. This will hold the seal more tightly against the crank and solve many leak problems.

[defiance]

I have a best machine block waiting to go onto my new short block.

The destructions say you'll likely need to have the mating surface planed about .010 if you've had a align bore / hone job.

This is a tech bit off the 440source site itself...   

As a tech tip, if you are having problems with rear main seal leaks, have your machine shop surface a small amount of material (approx. .010") off the bottom of the rear seal cap using their Rod/Main cap cutter. This will hold the seal more tightly against the crank and solve many leak problems.

Crap - never saw that on 440source.  I bet the machinist didn't realize it either...  I'd already have the engine at his shop for him to check if he didn't live 80 miles away...  None of the local machine shops work on mopar stuff.  Still, I'm sure they all have cap cutters, I'll see if I can find a local one to do a quick cut.

Thanks for pointing that out!

[RD]

that is how it should look


now... i put silicone between the seal and the block too, to ensure no leakage pasts between the two. ditto on the aluminum cap.

[defiance]

*sigh* - no luck.  milled it .010", put it back in, still leaks at the bottom center of where the cap meets the crank as soon as I start priming.  I did make sure to have plenty of silicone between the seal and the cap, engine and cap, and where the two seals meet, not to mention along the sides and mating surfaces.  Those seal up nice, though, it's just the seal>crank surface that leaks.  Guess it's time to take it back to the machinist. 

Man, this sucks.  I was planning on it being up and running on the test stand today...

Also, one thing I never considered about a girdle, they make main seal issues *MUCH* more of a pain!  I have to take the whole thing out to get to the cap.  With the girdle, the pan, windage tray, two gaskets and taking apart & re-assembling this thing 3 times now in the past week or so, I must've spent $20 just on RTV! 

[RD]

its your crankshaft then

moparguy01 had this same problem.. the hash mark area on your crank shaft is worn too much and is allowing seepage.  check that area for uneveness (is that a word?).

[firefighter3931]

This post looks familiar to another thread we had awhile back....same issues 

Look here : http://www.dodgecharger.com/forum/index.php/topic,34729.0.html

And some excellent tech advice from Challenger340 (Bob) : http://www.dodgecharger.com/forum/index.php/topic,35697.0.html




Ron

[General_01]

I used a stroker kit from 440Source and  a billet rear main seal from Mancini. My engine builder says that he sends all 440Source cranks out to have the end finished. He told me the name of the process, I just can't remember. He said he started doing this after he had three rear seals leak after he built the engine and that is what they found. If you want him to do your engine with a 440Source crank, this is an automatic on your bill or he won't touch it.

[defiance]

Alright, I'm going to pull the accursed thing apart again.  I don't think I'm going to put it back together unless I find a "smoking gun" that definitely would cause this; otherwise I'll just get it to the shop.  Man, that sucks, though - it'll be at least next weekend before I can get it there, and probably another couple weeks for him to get to it and fix it, and then I have to figure out when I can get back to pick it up....... 
(happy thoughts .... happy thoughts...)
Ok.  Anyway.  I'll pull it apart, clean it all up and get some close-up pics of everything to see if there's any obvious problem.  I'll also try to get some gap measurements with the cap in place.  I don't know if it's a geometry issue, installation issue, or a crank issue,  but I *REALLY* hope it's one of the first two.  The crank is brand new, so the hashed area shouldn't be too worn, but maybe it was too harsh or otherwise off?  Would that be obvious in pics?

[defiance]

Ok, some pics.  I couldn't get a caliper down in there, but I don't think it's offset. 

Yes, I know the RTV is MESSY on this pic, this was about the 4th time I put it back together, and at this point I was pretty sure it wasn't going to work, so I wasn't really trying to be neat

The pics are while sitting, then while priming, then looking down on the crank and upper seal with the cap off.

[defiance]

The pic kinda makes it look like the one on the right is more compressed, but I think that's a residual lump of silicone.  Look at the distances between the metal, if either is tighter it would be the left, but I think they're pretty equal...

Does the hashing look good?

[defiance]

Alright - went out and got some clay to check more closely rather than just "eyeballing" things.  The sides are DARNED close to equal - measuring crank surface to bottom of the seal seat on one side is .085", other is .083".  Not enough difference to care about IMO.

The cap, though, is trouble - Measuring either side comes out pretty equally at .093".  Top?  .102"

So I guess I need ANOTHER .010 taken off the mating surfaces?

[defiance]

Actually, I'm thinking about how much of a pain it's going to be getting the cap top to seal up against the girdle if I keep cutting it down ... A gasket would be more forgiving, but I gotta get it sealed against the girdle... Do you think I'd be ok putting a thin layer or epoxy in the bottom of the channel where the seal sits instead of cutting it more?

Ugh..  What a pain this all is ... 

[RD]

i really dont see anything wrong with that, as long as its pretty close to true.  better than making a shim on top of the cap to make up the space between the girdle and the cap.  But..., .020 really isnt that much and can be compensated with silicone IMO.

[turbobitt]

I have had leaking rear main seal and this is what I found.

1. The main studs often interfer with the seal cap. Make sure there is clearance between the top of the main studs and around the nut.

2. Some of these aftermarket caps are solid on the end facing the cap with the oil slinger clearance cut. The cap will mate flush with the main cap and not allow oil to drain from the slinger area. Oil pressurized from priming/running will overcome the seal and find its way on the floor if not allowed to vent. Note the open/profiled area in the factory seal retainer.

3 - If the crank was out of the engine, bolt the main cap and torque. Then bolt on the seal retainer with the seals and check alignment of the seal halfs. With the slop in the holes, it is possible for the halfs not to line up and sensitive with the rubber/neoprean knife edged seals. This is not an issue with a wide rope seal. With the seal cap slightly lose, you can line it up and scribe a line accross the top of the seal retainer and block to correctly assemble later with the crank in the block.

4 - 440 source cranks have a very aggressive knurle and may be part of the issue. May need to use a rope seal.

[firefighter3931]

My best guess is that the finish on the crank is causing the issues....pull it and have it poished to the right finish for proper sealing or you will continue to have the same problems. 



Ron