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Replace Rear Main Seal

51K views 27 replies 12 participants last post by  rmcomprandy 
#1 ·
Engine is out and on the bench. I had a leak and determined that it was the main seal. Might have been a mistake. But the engine is out, pan is off, main cap is off and now I would like to install a main seal without any further dissassembly. How to proceede? Thanks for your help!
 
#3 ·
Oil Seal

Thank You! I had done a search but I must have done it wrong? Anyway I did a new search and "WOW" did I ever learn about main seals. Funny thing, I had noticed an odd wear pattern on the rear main bearing (front into copper/rear still grey). And there was a reddish materiel between the block and cap. It was real thin and pliable. Someone else had struggled with this problem on this engine as the pan gasket had silacone and sealer all over it. I will use a FRPP seal, set the crush @ 010-015, new main bearings, Clean the cap on a sheet of glass and 600 grit, add a one piece pan gasket and call it good. All over the inside of the engine is this reddish colored coating. I'll bet it is from some sort of stop leak... Thanks Critter, I appreciate the help!
 
#6 ·
Thank You! I had done a search but I must have done it wrong? Anyway I did a new search and "WOW" did I ever learn about main seals. Funny thing, I had noticed an odd wear pattern on the rear main bearing (front into copper/rear still grey). And there was a reddish materiel between the block and cap. It was real thin and pliable. Someone else had struggled with this problem on this engine as the pan gasket had silacone and sealer all over it. I will use a FRPP seal, set the crush @ 010-015, new main bearings, Clean the cap on a sheet of glass and 600 grit, add a one piece pan gasket and call it good. All over the inside of the engine is this reddish colored coating. I'll bet it is from some sort of stop leak... Thanks Critter, I appreciate the help!
Glyptol? Its a coating to aid oil drain back.
Rob
 
#4 ·
I too am replacing a rear seal on my 460, I have a Fel-Pro seal to install, the seal is in a bag with the instructions on the bag - I would like some confirmation before I install this seal.

Instructions read;

"Make sure the parting lines of the seals are offset in relation to the Block Main cap line by 3/8"."

This is the first time I have used Fel-Pro seals, is this a normal procedure for them.

I have attached a picture I sketched up - can someone confirm that's what they mean, before I screw up a seal by not installing it correctly.


thanks

Wayde

 
#8 ·
I installed the felpro seal in mine... It didnt say anything about crush depth! make sure you got the seal in the right way (seal lip faces a certain way). Then I believe i used some black permatex RTV on the ends of the seal where they meet. that was about it, its a fresh stroker so new bearings then toqued the ARP studs to spec.

What is this setting crush depth? ugh
 
#11 ·
I just wanted to update. Apparenty I didnt **** the rear seal 3/8" and i had the original felpro rear seal package and it said nothing about the crush or cocking the seal 3/8". I got another rear seal in an engine gasket set and that rear seal package said to **** the seal 3/8" but said nothing about setting the crush.

I took a look at the stock ford rear main seal and put it in the cap and the block to check the clearances. Would you believe that the stock ford rear seal has the perfect crush of .010-.015". But the felpro replacement had over .055" crush just on the cap seal half alone. the bottom was just about the same.

I ended up grinding down the seal to the .010-.015" crush (more towards the .015" side) and put black RTV on the seal ends as well as the cap/block corners. I also cocked the seal 3/8".

Thanks to this thread i now know about rear seal crush. this thread also probably saved me from one hell of a rear seal leak. Thanks!
 
#15 ·
mains

You`ll have to loosen the other main caps to relieve pressure on the crank so it will drop alittle so can slide the seal in also depending if the seal has been replaced or not some had rope seals if thats the case there will be a titty that sticks down in the block to hold the rope in place that needs to be taken or broke out if not the neoprene seal will not seat...Bill
 
#17 ·
When adjusting the seal crush, should this be done with the seal dry or with the seal having been dipped in motor oil?

In any event, once the crush has been adjusted and the seal halfs are both offset by 3/8" and a dab of rtv has been placed on the seal ends, but just before the crank is installed and the bearings torqued, what, if anything (motor oil, assembly lube, some other type of grease or whatever), should be coated into the seals?
 
#20 ·
Thanks for posting this pain in the butt diagnosis and repair.I have a friend that has built a 545 -- A460 block street motor with a rear main leak that has been driving him nuts. Has done the meticulous assemble like most every one here has and it still leaks. I'm sure he hasn't addressed seal crush.

Thanks again ----- Qkiss
 
#21 ·
I just looked at the .015 blade of my feeler gauge. It is really, really thin. Can you really lay that on a surface and then trim down the rear crank seal crush to be that small and still see anything with your eyes anywhere near accurately enough?? I haven't tried this yet, but I can picture having real troubles grinding down the seal with a dremel tool to be accurate to .015 crush.
 
#24 · (Edited)
Use a FLAT file by hand. It is the steel ring within that seal which needs to be trimmed. along with the Nitrile rubber.
Be sure to trim ONLY the one side with the small bevel on the lip of each half-seal and not the side with the protruding lip.

EDIT:
You will see this under close inspection.
 
#22 ·
What type of grinding bit in my Dremel-like tool is best to use? The ones that look like conically shaped grinding stones? The ones that look like circular sandpaper? The metal bits which I think, but am not positive, also do grinding?

When you ground down your seals for the proper crush depth, did you grind them while they were pushed into their slots in the engine block and in the bearing cap or did you grind them while they were removed from the engine so you wouldn't risk contaminating the engine with debris from the grinding?

My engine is super clean and ready to be assembled and I hate the idea of grinding anything while it is near the engine and risking spraying all sorts of foreign matter including metal into the engine while doing the grinding no matter how hard I may try to cover the engine.

Question: If I marked each seal-half and used wire cutters to trim it down instead of grinding it with a Dremel tool, do you think that would work?
 
#23 · (Edited)
I gave this some more thought and if nobody else chimes in with a better experience, I'm going to position each seal half with one end flush with the block or the rear bearing cap, whichever applies, and use a hand file to trim down the other end that is sticking up so it sticks up by .015. I figure I can control a hand file the best and I can always file in a direction away from the engine to minimize how much junk will go into the engine that I'll have to clean out.
 
#25 · (Edited)
I see what you mean about the lip sticking up on one side and not sticking up on the other side. I did file the end with the non-protruding leap on one of the half seals, but I had already filed down the other half-seal before I saw your posting and it turns out that I filed down the end on that seal-half that had the protruding lip. However, even though I filed the wrong end, I got that end completely flat except that I left the protruding lip alone so it still protrudes exactly the way it did before I started filing the end.

Is that a fatal error? Should I get another rear seal because I filed the protruding-lip-end (even though I left the protruding lip alone) and do this procedure all over again?

Yours is the only posting I have seen in any of these threads that mentioned that one end has a protruding lip and the other end does not and that the non-protruding-lip end is the only end that should be filed(maybe I missed a posting that mentioned it?) and it is very, very good to know these small details.

Thanks very much
 
#26 ·
I see what you mean about the lip sticking up on one side and not sticking up on the other side. I did file the end with the non-protruding leap on one of the half seals, but I had already filed down the other half-seal before I saw your posting and it turns out that I filed down the end on that half-leap that had the protruding lip. However, even though I filed the wrong end, I got that end completely flat except that I left the protruding lip alone so it still protrudes exactly the way it did before I started filing the end.

Is that a fatal error? Should I get another rear seal because I filed the protruding-lip-end (even though I left the protruding lip alone) and do this procedure all over again?

Yours is the only posting I have seen in any of these threads that mentioned that one end has a protruding lip and the other end does not and that the non-protruding-lip end is the only end that should be filed (maybe I missed a posting that mentioned it?) and it is very, very good to know these small details.

Thanks very much
IF you have trimmed the adjoining half seal with the beveled end to be completely FLAT and both mating surfaces are flat, I don't think there would be an issue.

Another way to say it ... The bevel is there to accept the protruding lip from the other half but, if that bevel is completely gone it shouldn't make a difference it the lip half is also flat.
 
#27 ·
I did not know the protruding lip had been meant to match up to the bevel. But now that you mention it, that makes a lot of sense.

Now that I think more about it, it would make the most sense that if one is ever going to shorten either or both half-seals to always ensure that both ends of both half-seals are always flat so that they will mate together.

In my case, I'm now inclined to cut down the protruding lips so they are flush (flat) with the rest of the seal edge.

After all this analysis, we should award Phd degrees in rear seals!
 
#28 ·
I started paying big-time attention to the "make-up" and "crush" of rear main seals about 20 years ago when changing a Pontiac rear seal from rope to an aftermarket lip seal which just didn't work, out of the box.

"Good judgement comes from experience and experience ... well, that comes from bad judgement", Ben Franklin
That is true with just about everything.
 
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