4.6 Rear main seal, who's replaced it?
When I removed the engine in my 04 D2 it had a terrible rear main seal leak. After removing the flywheel, I saw why. The seal was cocked at an angle, and had walked back on the end of the crank shaft, the top of the seal was barely in the hole.
No big deal, or so I thought. After cleaning everything, installing new cruciform seals with Ultra Black RTV, I tapped the new rear main seal in place. It bottomed out just below the outer edge of the block, and appeared fine.
Fast forward to me trying to start the newly rebuilt engine(which didn't start, seperate issue), and the rear main seal is pouring oil again. Wtf?!
Enough so that the engine is coming back out, I'm not adding a quart of oil every week.
I've done many rear main seals in other engines, 1 and 2 piece, and never had a problem.
As I explained in another thread, the 4.6 has the worst rear seal design ever...ever.
The rear main cap is recessed 3" or 4" into the block, leaving a huge open cavity to fill with oil, with only the rear main seal to hold the oil in.
ALL the tolerances in my rebuild are within spec. So the rear main bearing isn't letting any more oil than normal pass through it.
I used the stock style, full cross, Bearmach cruciform seals too.
The tail shaft of the crank showed no visible damage either.
I can fix all the other issues with this engine and truck, but I cannot comprehend wth is going on with this ridiculous design.
The Rave shows/says nothing unusual either. Put the seal on the shaft, and press it into place.
I don't have enough bad language to express my disgust and disbelife in this design.
Anyone else had this problem?
Replaced a rear main seal and did anything special with it?
It'll be a few weeks before I get the engine back out, but I'm trying to find out any info I can in the meantime.
Thanks

 

 

Thank you sir, and you're right, it looks simple enough.
I'de like to know your opinion on the gap between the rear cap, and where the seal bottoms out, leaving the large cavity in between that I was talking about too.
Maybe I got the experimental pos engine that was never supposed to make it into a production truck...that would be my luck.

 

As for the cruciform seals, originally I got AllMakes, and they look like junk. They aren't even a cross shape. Just a straight line with a knot where the cross would go.
I never used them, and that's why I bought the Bearmach.
The Bearmach looked like stock, and appeared to seal perfectly.
I assume the oil is not passing the cruciform seals in my engine, but simply the oil passing between the crank and rear bearing, as it should.
That oil then fills the large cavity behind the seal, and the seal can't hold it back.
To me, the seal should fit flush against the rear cap, but mine bottoms out several inches before that.
The Rave shows the rear seal go in After the rear main cap with the cruciform seals too. As I had considered putting the next seal on the crankshaft, then putting the cap on.
But, since the seal bottoms before it could be pressed that far, I think it may crush/flex the outer seal enough to still make it leak, and possibly open the rear main bearing up enough to put it out of spec, and spin the bearing.
I don't know.
Thanks again.

 

Did you put a new front cover (oil pump housing) on this engine or mess with the pressure relief valve assembly? Now, I'm starting to wonder if the oil pressure relief valve is stuck, causing to much pressure...and holding the valves open (giving the impression it jumped time).

Had a 392 International gas engine I rebuilt years ago, full rebuild (pistons, heads, cam, etc, etc). Went to start it up, after priming the oil pump manually, hit the key and she started spinning, then faster than normal without even the remotest sign of starting. So, I'm thinking the parts store sold me the wrong cam or something. After a bit I pull valve covers and watch valve train work, looks good. Decide to check compression on number one, all good. So, I have the other mechanic keep cranking it over while I check the rest...but as I go along...the valve train stops moving and the compression starts to diminish at each next cylinder...eventually, reaching zero.

Ended up, oil pump relief valve was stuck and the pump was creating full pressure...to the point it actually floated out the valves (hydro locking the lifters). Let the engine sit for a bit and it would produce compression for a few revolutions...then gone. Replaced oil pump...me...all happy again and good with my sanity.

Just food for thought...

Like that insurance thing...after forty years..."we've seen a few things" .

But, other than that...I see nothing wrong with your installation of the rear seal (granted, I like the ultra gray).

Brian.

 

Yes sir, a new front cover and oil pump.
Oil pump primed with vaseoline and assembly lube, loc-tited and torqued inner pump cover posi-drive/phillips heads. But, I have not checked to see if the pressure valve is functioning correctly.
Maybe I'll get lucky there, but regardless, the engine has to come out to replace the rear main seal.

Have you replaced a 4.6 rear main seal?
If so, did you see the huge gap between the rear main cap, and where the rear seal bottoms?
And according to the picture in the Rave, the seal should bottom just below the rear block surface, which it did...still leaving the several inch gap to the rear cap.
That's the real problem that I can't understand.
And I'm 41, and happily a Former proffesional mechanic from years ago. I'm all ears on 40 years of mechanic work and years of LR ownership. So thanks again for your input.

 

 

Thank you sir...and lucky you

 

Rear main seal when I first removed the engine.
If you look above it, you'll see the block surface recessed several inches above the seal before the block goes vertical to the lower intake.
The back of the rear main cap is that deep in the block.
All that space around the tail shaft of the crank is an empty void.
There is no pressure against the rear/block side of the seal. Only pressure around it's outer edge, and the small lip that seals on the shaft.
If the seal sat flush against the inner rear cap, that cavity could not fill with oil.
As for the original bad seal, it could have been installed incorrectly, I don't know. The new seal I put in, bottomed out flush, and appeared to be installed correctly, all things considered.
I'll know more in a few weeks when I get the engine back out.

 

Ok, F this stupid picture loader...Again!!!
RRRRRRRRRR!!!!!!!!!!!
Now, after minutes of waiting, the forum will only allow me to upload pictures I've taken in the last month.
I'm done trying. This site functions as bad as my Land Rover does!!!