IMPORTANT question — Crankshaft Rear Main Seal TagsNone

[seafish]

Pulled the old SBC clutch today and found the rear main seal seeping.

After gently prying out the seal and in the process of gently cleaning up the case and crankshaft with brake cleaner, I can see and feel some extremely, very slight markings on the crankshaft seal surface.

After cleaning the crankshaft sealing surface with 1500 and 2500 emory cloth and soapy water, the marks are still there but I can not really feel them, even with a dental pick.

ALL of this was done with starter mounting/rear bell house mounting plate still bolted in place!!!

Of course, I am hoping NOT to have to pull the starter, rear housing and inner seal housing in order to fix this, though obviously I will if I have to.

My question is — Exactly what do I need to do to ensure this wont be a problem before and after installing the new Cummins rear main seal, which I already have in my possession.

Pics—

 

[seafish]

Pix after cleaning with emory cloth and soapy water—

 

[seafish]

After even more careful inspection, using both 13/32" (.4062") and size X (.397") machining bits that I had on hand, it seems that the inner seal housing that surrounds the crankshaft is off center.

I can easily fit the larger bit (.4062) into the sapce between it and the crankshaft between 7 and 11 oclock, while the smaller bit fits in between 12 and 6 oclock.

The wider opening also corresponds to where the seal was seeping more (see 9 to 10 oclock at first pix in first post).

I have already read how the inner seal housing does NOT use any alignment dowels and some people have found it offset from the factory by even up to .009" (90/1000's")

That said, STILL trying to avoid having to buy and use the Cummins Repair Seal #3926126 if possible simply beacisue I already have the regular Cummins replacement rear main seal and would like to continue to make progress over the weekend.

All expert opinions are welcome, but it looks like Im gonna have to dive deeper into the rear of the engine then I was hoping to.

 

[petersonj]

I did my first clutch job on my truck at 297,000 miles. I saw that the rear main seal was seeping, similar to yours. I did no measurements. I installed the seal below from Napa. I installed the seal only.

The original clutch did not fail, but the pilot needle bearing disintegrated and damaged the surface of the pilot bearing area on the transmission input shaft. Fast forward to a few years and 90,000 miles later, I replaced the clutch with a South Bend 1947-OK-HD organic clutch. The new flywheel uses a sealed ball bearing which makes me feel much better regarding the damaged transmission input shaft. Getting to the point, the rear main seal was bone dry.

I know that you are welcoming expert opinions, but I just had to throw mine in there, anyway.

- John

 

[seafish]

I did my first clutch job on my truck at 297,000 miles. I saw that the rear main seal was seeping, similar to yours. I did no measurements. I installed the seal below from Napa. I installed the seal only.
View attachment 141706

So to clarify, you pulled out the old seal and replaced it without removing anything else (ie starter and bell adapter plate and inner seal housing)??


FYI— the pilot bearing on the SBC ConOFE on the clutch that I pulled is still good, but the throwout bearing has been dry and noisy for awhile now. Strangely enough, the Feramic side of the Con OFE wore into the flywheel substantially … not even in a flat way, but in sort of a light "V-shape" over the width of the Feramic clutch facing…NO idea why that happened, but installing a Valair dual disc quiet organic street clutch this time.

 

[petersonj]

So to clarify, you pulled out the old seal and replaced it without removing anything else (ie starter and bell mounting plate and inner seal housing)??

That is correct. And, the Napa seal was an FTPE style, installed dry. Just to clarify, this was on my 2002 truck. I don't think the 2005 or 2005.5 year (NV5600 vs. G56) is any different, other than the seal part number.

I think that you will like your dual disc organic clutch. My single disc organic South Bend clutch is very smooth, responsive, and good for 900 lb/ft torque - my tune probably puts me around 650 lb/ft torque.

- John

 

[PLohr]

@seafish :
I wonder how much off center the rear main seal / adapter can be before it starts leaking. Yours is 0.0092" off center. That's about half of 1/64".

Do you know about Torque King 4x4's TS6000 rear main seal installation kit? It comes with a steel ring for centering the rear main seal housing.

https://torqueking.com/product/6000...r-main-crank-seal-install-tool-set/#topOfPage

I used the above kit including the centering ring don't remember if I checked how well centered the rear main seal housing ended up.

 

[seafish]

Just talked with Genos and they highly recommend re centering the inner seal housing to get a proper seal.
Pulling the transmission adapter plate and inner seal housing will also let me get better access to the crankshaft seal surface for cleaning with emory cloth… so thats what Im gonna be doing over the weekend.

 

[sag2]

Pulling the housing is the correct repair, but if the seal made it 19 years I would have stuffed a new one in and be done with it. Even if it only lasts 9 years! From the photo it looks like it hasn't actually leaked, just weeped and clutch material and dirt were attracted to the oil.

 

[seafish]

Got everything on the rear of the block further taken apart and cleaned up today while under the truck.

Everything went smoothly EXCEPT one of the four rear oil pan bolts which are necessary to remove on order to pull the seal housing was galled or frozen. Strangely enough, the first 3 bolts unscrewed easily, but the last bolt was just frozen tight. When moving up the big guns and using the 10mm 6 point with a 1/2" breaker bar on it, I couldn't tell if the little bit of movement I was getting was the bolt actually turning or breaking… SO it was back to PB Blaster and a gentle torch SLOWLY working it in and out until it almost imperceptibly started to move, after which I simply worked it in and out less then a 1'8" at a time to clear the threads and get er done!!! SO glad I was careful and slow and didn't break the LAST bolt !!!

Then it was on to cleaning and polishing the crankshaft sealing surface and lightly cleaning the rear of the block and top of the oil pan gasket. I had seen so many YT certified mechanics just tearing the rear oil pan gasket as they pulled the inner seal housing off, so I simply used a sharp utility blade and scraper to separate the gasket from the bottom of the seal housing BEFORE removing the housing and it came off cleanly leaving the oil pan gasket 99.9% intact on the oil pan.

Pics or didnt happen —

 

[seafish]

 

[seafish]

Seal housing off and all cleaned up—

 

[seafish]

Crank sealing surface cleaned and polished with 400 to 1500 wet/dry paper.

BEFORE—

AFTER —

 

[seafish]

ALSO removed the top rear freeze plug in order to install the Fleece Bypass Coolant thermostat/housing in its place to help keep #5 and #6 pistons cooler under load. I have had this kit on the shelf for years —

Needed to clean the opening and found that a 1.5" PVC cap with a piece of wet/dry paper wrapped around it and a quick spray of soapy water worked perfectly— ran it from 400 to 1500 grit …overkill, I know, but its what I was using anyways.

Freeze port cleaned up —

And Fleece Bypass housing trial fitted —

 

[seafish]

Will be back at it tomorrow, but thankfully on the putting it all back together side !!!

 

[seafish]

Yesterday was a holiday but made solid progress today.

1) Got the Fleece coolant bypass fully plumbed up to the Fleece riser at the OEM thermostat housing. FYI — This is a very well designed and built kit.

2) Got the Larry B starter rebuilt kit installed while the starter was out. This is ALSO a very well designed kit that comes with all necessary quality parts, instructions, gloves.. and even a band aid … I guess just in case you slip with the screw driver while taking the starter apart.

3) Got the inner seal housing installed in mathematically perfect alignment with the crankshaft by using 10mm machine drill bits as feeler gauges. The 10mm drill bits measure .373" diameter and I used 3 of them to align the housing around the crankshaft before fully tightening the housing down. I took a little time to slowly tighten the bolts on the housing and the oil pan, while checking for clearance with the drill bits, and at one point I even used a brass hammer to tap the housing around a little, but overall it worked out perfectly.

Obviously I installed a new seal housing gasket, but I also used a short smear of Permatex RTV in order to seal the crucial corner areas where the engine block, seal housing and oil pan ALL come together. Also added a LIGHT coating of Permatex on both sides of the old oil pan gasket, after cleaning it with acetone, in order to help it seal up again.

Pix—

 

[seafish]

Waiting for the RTV to cure and the camshaft seal to arrive so I can install the actual rear main seal, the starter, the adapter plate and maybe even the new clutch … hopefully tomorrow.

 

[User113]

Is this where you can stack two seals?

 

[BigPapa]

Is this where you can stack two seals?

No. That’s the front.

 

[seafish]

@sag2

or @everyone

I am having no luck finding an actual torque value for the six 8mm bolts that hold the inner seal housing to the rear of the block. This is the same housing that the 4 rear oil pan bolts also screw UP into.

The oil pan bolts are rated at 21 ft pounds but they are a slightly larger size then the seal housing bolts (but which also have a 9.8 stamped on their heads) … I am gonna GUESS that the 8mm bolts need to be torques to around 15 ft lbs each, but would LOVE an actual, informed torque value … if possible.

TIA