Replacing 8V71 Main Seal

Glennman · March 09, 2020, 08:32:40 PM

Fired up the bus yesterday after replacing the thermostats, installing a block heater, and bleeding the system by driving it around a bunch of times. As with most old Detroits, I have the typical leaks in various places, but I have mostly grown used to them. However, the seal at the end of the crank really bothers me, as I now have a small puddle of oil showing after running it for only a few minutes, probably about 3" across. The book shows the seal, and mainly recommends removing the housing there that surrounds it.

But, there is a note that states that the seal may be removed by drilling small holes in it at opposing sides, installing some sheet metal screws with washers, then using a prybar, pulling the seal out from the outside without removing the housing (oil pump housing if I recall correctly).

Has anyone ever tried this? Or, has anyone had any success with this? Thanks, Glennman

luvrbus · March 10, 2020, 05:52:52 AM

I have used self tapping screws for many years to push the seal out that is the easy part,removing and replacing the wear ring on the end of the crank can be challenging.with the bellhousing in place

Glennman · March 10, 2020, 09:29:50 PM

Thank you luvrbus. From what the book says, one would run the screws in with washers, then pry against the washer. It sounds like you are running the screws in until they hit, then keep turning until the seal slowly rides up the threads (?). Also, does the wear ring always have to be replaced? I didn't know there was one... sounds like a challenge.

Thanks again. I'll be starting a new thread on a radiator problem I'm having now. It never ends.

luvrbus · March 11, 2020, 06:05:42 AM

Quote from: Glennman on March 10, 2020, 09:29:50 PM
Thank you luvrbus. From what the book says, one would run the screws in with washers, then pry against the washer. It sounds like you are running the screws in until they hit, then keep turning until the seal slowly rides up the threads (?). Also, does the wear ring always have to be replaced? I didn't know there was one... sounds like a challenge.

Thanks again. I'll be starting a new thread on a radiator problem I'm having now. It never ends.

I do it with washers and screws or screws only depending on how the bellhousing is made ,some don't have the flange (stop) to push on they free float so you need the washers to pull it,the wear sleeve is a roll of the dice if the engine has one I always change it or install one if not equipped that is a lot of work to take a chance on IMO

buswarrior · March 11, 2020, 10:00:39 AM

Not to be an @$#...

Your puddle is not from an airbox drain, or otherwise masqurading as a crank seal leak?

I hate fixing the wrong stuff...

Happy coaching!
Buswarrior

freds · March 11, 2020, 03:22:08 PM

Quote from: buswarrior on March 11, 2020, 10:00:39 AM
Not to be an @$#...

Your puddle is not from an airbox drain, or otherwise masqurading as a crank seal leak?

I hate fixing the wrong stuff...

Happy coaching!
Buswarrior

Ah, good point. When I am trying to find a leak I first pressure wash and then stuff paper towels all over the place to narrow down the source.

chessie4905 · March 11, 2020, 03:32:34 PM

Spray talcum powder helps to pinpoint smaller pesky leaks.

luvrbus · March 11, 2020, 04:11:31 PM

LOL the rear main seal is the easiest leak you will ever find

dtcerrato · March 11, 2020, 04:22:36 PM

I like the talcum powder trick. After a gravel hwy run in AK the engine looked like it was fillet rolled in flour. I took photos because of the easy view of where the leaks were at. Them photos enabled me to get the ole' 2 stroke as dry (close to leak free) as is been in four decades of ownership - soooo, 10-4 on talcum!

luvrbus · March 11, 2020, 04:56:10 PM

Quote from: dtcerrato on March 11, 2020, 04:22:36 PM
I like the talcum powder trick. After a gravel hwy run in AK the engine looked like it was fillet rolled in flour. I took photos because of the easy view of where the leaks were at. Them photos enabled me to get the ole' 2 stroke as dry (close to leak free) as is been in four decades of ownership - soooo, 10-4 on talcum!

There are lot of high $$ gadgets on the market I have one but plain old bleached while flour works for me ,lol after so many years you know where they are gong to leak

chessie4905 · March 11, 2020, 07:43:04 PM

I'm not allowed to touch wife's flour.

luvrbus · March 11, 2020, 07:49:47 PM

Quote from: chessie4905 on March 11, 2020, 07:43:04 PM
I'm not allowed to touch wife's flour.

They do get touchy Sonja asked me one time do you want yeast or baking soda to go with it

chessie4905 · March 11, 2020, 08:27:14 PM

Haha.