NHC 250 front main seal

[Bandit02]

My front main as leaking so I tore into it today. I got to the point where the harmonic balancer mount on the crank needs to be pulled off and I can see the seal behind it. Looks simple enough to replace when I get the correct puller. The seal sits in a round bracket inside the 2 piece front engine mount, is this bracket supposed to be flush with the engine mount? Or on an angle as shown? Perhaps the source of the leak.

 

[WillWagner]

Are you referring to the little bit poking out past the trunion? If so, all that is the bushing on the front cover. The trunion is the front mount, there should be rubber between the cover and the mount. It looks in tact and normal. Getting the adapter off is a mofo.

Did you wash it first? Sure don't look like the seal is leaking. It takes a special tool to remove and install the adapter and one for the seal removal and installation.

 

[WillWagner]

I'll look and see if I have a book for it and scan the image of the tools. I might have a seal tool.

 

[Bandit02]

Yes sir I washed it first. I cruised the net looking for cummins special tools and never came across any from Snap-on, etc that were specific in pulling the adapter off, is it pressed on? I thought maybe a generic 5 ton puller would pop it off.

Ok so the bushing is normal like that, perfect

The leak was getting progressively worse over time. I just finished repairing a leak at the air compressor mount, they used RTV silicone and not a gasket. Bought a special wrench from snap on for that PITA inside bolt. Slowly but surely knocking them off

 

[WillWagner]

I looked for a bit but can't find one. I'll keep looking. IIRC, the crank nose is tapered, it comes off with a good pop and I THINK it needs to be lapped when installed. Like I said, i'll keep looking, I know it is around here somewhere....

 

[Bandit02]

A generic puller can't pop that off? What's special about the actual one I need?

 

[WillWagner]

Sorry, been a baaad weekend.

The crank nose is tapered. You could TRY and use a puller, but if you have ever removed something from a tapered shaft that has been torqued on, you will know that the pressed on part WILL come flying off. Do not be in it's path. When installing, you need to use extra fine lapping compound and lap the nose of the crank to ensure you have, IIRC, 75% coverage or the adapter will come loose.

 

[Bandit02]

Used a 7 ton jaw puller today and a few good whacks with a big brass hammer and POP off it comes flying. Seal in there is a CR 31185. The inside surfaces of the tapered hub, and the crank nose were shiny and clean. Now I need to order a new seal.

Once the new seal is installed (there is no lip in which the seal rests against so a installer tool is preferred to make sure the seal sits even & flush). The hub bolt is a lubed grade 8 3/4-16 UNF which will need to be torqued to 315 ft lbs.

From what I've researched these old tapered noses where the Achilles Heel of Cummins back in the day because sometimes when these hubs were rusted on and removed they were sometimes known to break the nose right off.

Oh, and that CR/SKF 31185 seal sells on Ebay for between $16-19, just FYI.

 

[WillWagner]

Very good! Glad it came off easily.

 

[fyrman1]

Used a 7 ton jaw puller today and a few good whacks with a big brass hammer and POP off it comes flying. Seal in there is a CR 31185. The inside surfaces of the tapered hub, and the crank nose were shiny and clean. Now I need to order a new seal.

Once the new seal is installed (there is no lip in which the seal rests against so a installer tool is preferred to make sure the seal sits even & flush). The hub bolt is a lubed grade 8 3/4-16 UNF which will need to be torqued to 315 ft lbs.

From what I've researched these old tapered noses where the Achilles Heel of Cummins back in the day because sometimes when these hubs were rusted on and removed they were sometimes known to break the nose right off.

Oh, and that CR/SKF 31185 seal sells on Ebay for between $16-19, just FYI.

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Any particular specs on the jaw puller length depth etc?

 

[Bandit02]

I rented it from a local parts house. Any will do as long as it fits over the hub.

 

[fyrman1]

And how did you manage 300ft lbs?

 

[simp5782]

Thought I would add some pics since not all of the seals sit that far out on the mount like that Some are actually recessed in housing like on a scrap engine I have and some are flush like on my engine when I took it off.

Mine was a little stuck more than most. so I snuck a crowbar thru the wire harness hole on the drivers side and wedged it between the two jaws since I could not get an impact in there to hold it since I was rotating the engine.

I install the seals with a 1/2" drive extension using the female side to seat it square to the housing evenly with half on the seal and half on the housing and then to seat it further down by moving it to the inside on the seal

Picked up a Cummins seal from a surplus guy for $5.
Napa # 59997
Oreilly/National # 39807
Cummins # 208069 on eBay for under $20