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main bearing side seals?


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when I rebuilt my L18 I re-used the old main bearing side seals - because I couldn’t get the new ones into the grooves in the main bearing cap – probably my inexperience, but even with a pin punch and hammer they were too tight to go in. So, now 40k miles later I’ve got a serious oil leak down the engine plate between the block and the bell housing.(I’m assuming it’s the main side seals and not the rear main seal gone bad) I want to try a fix with the motor in the vehicle. I see it has been done on Datsuns - see http://www.classiczcars.com/forums/thread41742.html

I would appreciate any warnings or tips on the job? I’ve got a tube of Locktite Grey silicone - which everyone says is the best - and a new set of side seals. But if I couldn’t get it right with the motor on the bench, what are my chances of getting it right while lying under the truck with oil dripping in my face! thanks for any advice

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thanks Hainz. My seals are two pieces - one on each side of the bearing cap. I got the oil pan off, and I can't see if it's the side seals or maybe the rear crank seal. The oil dripping in my eyes didn't help!

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the way i do it is with the cap off..put a light dab of RTV where the seal will contact block..i set the seals up in place and with seals sticking down lower than the bottom of cap..."about half way out the bottom of cap"..get your cap in place and aligning your bolt holes slide it in place and evenly tap in slowly with a plastic hammer(i use steel) lightly tap into place...

when you've got it close enought to bolt holes use the cap bolts to "pull it down" to block slowly and evenly...the seal will touch the block and come up on it's own!! walla your done!


this way is the best i've gotten it to work for me! trying to tap them in after torqing the cap in place hasn't worked out good for me..

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Also...take notice of the position of the cap. I should be flush with the back of the block....but....install as it was prior

The side seals are slightly longer than needed....and will need to be trimmed flush

As seen with the seal on the right




If the cap isn't removed yet....here's a little trick

Bolt in the center....prybar



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I personally have always just had a tube of black silicone that goes in a caulking gun, cut a nice 45 deg. tip, an fill those voids with just silicone, until you can see light through it. Never had a problems with it, and have done more than a few motors. You have to use a caulking gun though, use a far amount of pressure, works great...

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