MEL Rear Main Oil Seal, Lesson Learned

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TonyC
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MEL Rear Main Oil Seal, Lesson Learned

Post by TonyC »

Hi, all,

I just thought of something I learned about the MEL rear main seals during the rebuild process, and I wanted to share it with everyone. I'm sure that everyone who has done that sort of job has run into exactly the same issue with the new seals: The pins that are supposed to go into the side seals are just too thick to hammer in place, usually resulting in twisted pins. With every rear seal I installed I had just that problem, and I could not understand why...until now.

You know that the pins are supposed to go inboard of the main bearing cap in order to press the side seals firmly against the block. You also know that using small amounts of black silicone is called for where the neoprene seals are concerned. However, what nobody knows, to include me until this rebuild, is that the indent along the inner side of the side seal is too small for the pins to drive into. That is why, nearly every time, if you try to drive those pins in, no matter how careful you are, you will bend the pin and, in some scenarios (like mine this last time), spear the side seal, basically botching the whole wretched job. When that happened to me, I happened to have a spare set of side seals that came in a complete-gasket set I had on hand and was using in the rebuild. There was good stuff and bad stuff resulting with that: The inboard indents were large enough for the pins to drive in perfectly; however, the side seals were too short for the 462 application. I compensated for that length by cutting some intact segments from the ruined side seals, boring out the indents with my Dremel, then inserting them with black silicone applied, and trimming them flush with the block once fully inserted. So far, there has been no sign of oil loss through that seal. For some reason, the side seals Fel-Pro supplied with the gasket set, although about a quarter-inch too short for a 462, had exactly the right-size inboard indents; whereas the side seals of every rear-seal set sold by every Usual Suspect and then some do not have the right-size indents (they are just too small for the pins, every time). The fix is to carefully shave the indents larger with a Dremel cutting wheel to the point that the pins can go in with little resistance (some, yes, but little). This of course will require test-fits before going to button up the whole thing; once it's done just right, apply the black silicone to the seal, sink it in the bore between the bearing cap and block, drive in the pins carefully (they should now go in with little more than taps of the hammer), cut flush any excess, button stuff up to specs, and that should be the end of it.

A little tidbit of advice for anyone who may find themselves facing that job.

---Tony
Last edited by TonyC on Sat Jul 02, 2022 5:22 pm, edited 2 times in total.
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1966 Continental Sedan, affectionately known as "Frankenstein" until body restoration is done (to be renamed "General Sherman" on that event)
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Re: MEL Rear Main Oil Seal, Lesson Learned

Post by Solid »

I'm looking at probably having to do this on my 430, is it the same kit and do the same issues apply?
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Re: MEL Rear Main Oil Seal, Lesson Learned

Post by TonyC »

Honestly, I'm not sure. The Fel-Pro engine-gasket set I had on hand for the rebuild was supposedly compatible with both engines, and for the most part it was. But those side seals were just too bloody short (to say nothing about the rope sections for the crank, which naturally I did not use). The side seals of every rear-seal kit I got separately were always of the right length, but the indents (or trenches) were always too bloody small for the drive pins to fit. I'd say that, for length purposes, it's best to go with those separate rear-seal sets the Usual Suspects sell, but keep in mind that the trenches for the drive pins need to be enlarged before putting them in place. That actually should be easier to do than to try and lengthen a seal that's too short.

I'm pretty sure I will have to do that job again myself in the near future. The engine is still losing oil from the back, though the loss is a lot slower now than it was before the rebuild (I'm sure part of that is because the oil is also not being pushed out of every orifice by combustion gases leaking into the crankcase through blown-out pistons and rings).

---Tony
"Don't believe everything you read on the Internet, just because there is a picture with a quote next to it." (Abraham Lincoln, 1866)
"Question Authority!"

1966 Continental Sedan, affectionately known as "Frankenstein" until body restoration is done (to be renamed "General Sherman" on that event)
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