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401 crankshaft rear seal replacement


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On 11/18/2020 at 11:28 PM, telriv said:

Yes, Paul I have done many with the new seals I have in stock.  Used to even do many rope seals.  The new ones are so much easier.  What year car are we workin' on????

...with transmission still in as well? For a ‘65 Riv with a 401 ...is it a two piece seal ?

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     OK, here goes & pay attention as it will take me at least two hours with one finger typing, probably three. 

1st. remove the two bolts holding the L & R motor mounts. One on the top on each side can be reached from the top inside the engine compartment. The bolts should have a 9/16ths. head.

    IF you have A/C either remove the fan blade, 1/2" nuts & the shroud, 1/2" bolt, OR at least loosen the shroud so that it's movable to some extent as the fan blade rises. Best to remove just in case so the shround doesn't get damaged.  IF you DO NOT have A/C put the fan at it's widest spacing so as NOT to contact the finger guard.  You could ALSO remove the distrinutor cap at this time & lay it to the side & NOT between the firewall & distributor.


    Now raise the front of the car high enough to get yourself & a jack under the car. DON'T FORGET GOOD JACK STANDS!!!!

Next is to drain the oil in a suitable container.

    Remove the two bolts in the middle of the engine mount on the bottom which will ALSO have a 9/16" head.

    Get a piece of wood, 4x4, or some other suitable lifting device  a suitable length & put it under the harmonic balancer & jack up the engine as high as possible.  Keep an eye on the lower radiator hose because as you are jacking up the engine the hose needs to be long enough to NOT pull the soldered hose connection out of the radiator.  Just in case you MAY want to drain the radiator while up top so IF you do have to remove the hose the cooling system is drained already, BUT be careful as ALL the coolant will usually not drain completely & IF your not ready can make a mess.  IF it has the correct lower hose usually this is not normally nec. You shouldn't have to worry about harming the balancer as you will only be holding it up for a very short period of time. Get two small pieces of 2x4 x about 3" long & put between the mount & the frame of the car. May ALSO need a thinner piece of wood, 1/4" - 3/8" to take up any remaining space.  Now let the engine down on these blocks of wood.  This should only take a few minutes IF you already have pieces of wood done beforehand.

    Next remove the flywheel cover/dust pan.

Remove the two bolts holding the idler arm, 9/16" headed bolts, to the frame & pull down on the idler arm which will ALSO move the steering linkage out of the way. If the front wheels are off the ground the wheel will move easily. IF not you may want to jack up the right side only to get some movement out of the linkage.  This will give you enough clearance to remove the pan.

    Of course the last step is to remove the bolts holding the pan in place & remove.

Next is now the rear main seal. Remove the rear main bearing cap which will have 3/4" headed bolts. This cap is pretty tight into the block so either use the cap bolts to move the cap by wiggling it untill it comes loose or using two bolts into the rear main cap where the oil pan bolts were & use a slide hammer of some sort to help it out.  It's NOT nec. to loosen up the other 4 main caps.  In actuality the new seal is easier to install than removing the original rope seal.  Get a long enough sheet metal screw & screw it into the middle of the old rope seal at least 1/2"-3/4".  Be VERY CAREFUL NOT to do ANYTHING to "Nick" the crank. Now while turning the engine in a forward motion grab the screw with a pair of vise grips & while turning the engine over pull on the vise grips at the same time.  This should remove the upper part of the seal.  Some are easier than others to remove. Patenoits here is the  key word. 

    One of the things I like to do is take a center punch & hit the seal area kinda hard in 6-8 places to make raised marks in the cap to help to hold the seal in place to keep it from spinning. Others sometimes don't agree with this, BUT is the way I've done it for years. IF nothing else it gives me a warm feeling that I MAY have prevented a future problem. Next is installing the upper part of the rear main seal into the block. Spray the upper area with a suitable cleaner like Brakleen to get out an remnents or other debris out of the top sealing groove. Try & run a lint free rag through the groove & spray it AGAIN until it comes out CLEAN.  In the package the seal comes in is a piece of plastic that's called an installation aid. USE IT!!!!  It prevents the back side of the seal from being "Shaved" on the block upon installation which will now be not as tight as it should be for the nec. sealing.  Next put a very thin coating of grease or oil on the lip of the seal. Some may ALSO not agree with this, BUT I ALSO use an "ANAEROBIC" gasket maker sealer on the back side of the seal & on the very ends of the seals. It's made by Locktite item #51813 or Permatex part number PX51813 & is readily available at most auto parts stores.  I just rub a very thin finger swipe along the back side & just a small dot on each end. The lip of the seal needs to point towards the front of the engine or oil side. IF it's put in incorrectly it will surely  leak. With one hand & fingers install the little tag from the installation aid up into the block & with the other hand put the seal up against the crank & compress the seal lip with your fingers & start sliding the seal into the upper grove. AGAIN, others may NOT agree with this, BUT I ALWAYS install the seal with a 1/4" overlap to keep the mating ends of the seals from the parting lines of the block.  Next of course is the seal in the cap. ALWAYS remember the sealing lip faces the front of the block or oil side.  Put a thin finger swipe of sealer on the rear of the seal & a very small dot on each end with the 1/4" over hang.  

   Next is to install the rear main cap into the block.  This can be tricky as you need to install the side seals to the cap while installing the cap. Let the side seals hang out of the cap towards the block about  1/4'".  IF you put some of the Anaerobic sealer on the side seals it will make it easier to slide into the grooves. ALSO put some of this same sealer to the mating parts of the block on the cap to help seal this area. You don't need a lot just a finger swipe enough to make the cap slide easier to mate to the block.  Next is to torque the cap to specs.  Lastly install the "Nails" into the holes into the side seals. They are just there to help "tighten" things up & usually go up into the side seals pretty far. Sometimes a little bit of the nail hangs out. You don't have to worry about it as when you tighten the oil pan bolts it will try to compress the Nails even further. 

    Install  a new pan  gasket & tighten the bolts to spec.

Reverse the removal procedure to get EVERYTHING back together & follow the torque specs for ALL the removed components. IF the cooling system was drained nows the time to refill. Start the engine & try to let it idle before the revs come up.

Good luck.  I've tried to explain the procedure to the best of my ability.

Hope EVERYTHING goes well.


Tom T.



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  • 2 years later...



wonderful explanation on how to replace the rear main seal. I replaced mine not long ago (with a seal I bought from you), but I recall removing the oil pump pick up tube as well. Is that correct, or am I remembering it wrong?  Thanks.                       

Seattle Rick

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For anyone interested I have the seals in stock & ALSO send some of the sealer in the package.

The cost is $50.00 plus shipping.

It's NOT normally nec. to remove the pick-up screen.

Send payment to, personal check, bank/cashiers check, money order, made out to myself:


Tom Telesco 

12 Cook St.

Norwalk, t. 06853-1601


Tom T.

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@telriv Not trying to make this difficult but how do I know what shipping is going to be? Is there any way to do it more efficiently? I'm in a little bit of a hurry. I'm a High-school autoshop teacher and we are trying to get the car ready for the school car show next Saturday the 17th.

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