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Old 03-03-2023, 17:46   #1
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perkins 4108 rear seal - isnt it just ptfe stuffing rope?

Rebuilding a 4108 and curious about the "magical" rear main seal fix, looks just like ptfe stuffing box packing!

Can someone prove me wrong or right?

and what size? 1/4"? i have everything apart at my shop - might check measure the original rope seal and match some ptfe packing-
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Old 03-03-2023, 18:28   #2
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Re: perkins 4108 rear seal - isnt it just ptfe stuffing rope?

some were graphite impregnated and I believe the more recent ones are PTFE but there is a major difference in that the stuffing box packing is square and the perkins packing is tapered to fit in the groove. I guess if you were in a remote location , say, Chagos you could use ordinary stuffing box packing to get you home but the risk is that you'll apply too much or too little pressure the crankshaft sealing worm. the Perkins seal seems to always be exactly right if its really well rolled into the seal carriers. PLUS, the worst feeling in the world is when you finally get the engine all back together and in the boat only to find that the rear seal is leaking....avoid that moment by using the OEM seal.
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Old 03-03-2023, 18:49   #3
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Re: perkins 4108 rear seal - isnt it just ptfe stuffing rope?

https://www.parts4engines.com/perkin...l-upgrade-kit/

Is how little you might save worth the time it will take to do it over if you get it wrong? If done right the above seal kit works well.
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Old 04-03-2023, 06:08   #4
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Re: perkins 4108 rear seal - isnt it just ptfe stuffing rope?

well im based in the US, surely i dont have to order something so basic from abroad. Seller here wants $120!! unbelievable imo, esp since its just a readily available material..
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Old 04-03-2023, 06:23   #5
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Re: perkins 4108 rear seal - isnt it just ptfe stuffing rope?

I have ordered stuff from the UK. UPS and or FedEx don't care. I've ordered stuff from Germany. Same deal, it arrives just the same. I believe a lot of items these days originate in China. Global shipping seems pretty common.

As an example, you can get butyl tape from lots of places. Just because it's butyl tape doesn't make all butyl tape the same. Some lasts seemingly forever. Some lasts a year or two. Both are the same stuff, right?

I'd buy something known to work from a reputable supplier. You do your boat. Might work out fine, might not.
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Old 04-03-2023, 06:56   #6
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Re: perkins 4108 rear seal - isnt it just ptfe stuffing rope?

I installed an Air Sep kit on my 4108. Basically it is a venturi in an air filter. It puts the crankcase under a slight vacuum, like the PCV system in a gasoline engine. This offsets pressurization of the crankcase due to any blow-by that might be present, so oil isn't pushed out of the rear main when running. In a lot of boat installations the rear main seal is usually low due to the need to accommodate prop shaft angle so the oil level is high relative to the rear seal.
Another benefit is a somewhat quieter intake. I saw a 3 db reduction in my saloon at cruise RPM. Also you get a real air filter to replace the stock gravel strainer Perkins supplies.
A little off topic of seal type, but it is a product I have been pleased with, and it eliminated a slight rear main seal drip in my boat.
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Old 04-03-2023, 07:08   #7
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Re: perkins 4108 rear seal - isnt it just ptfe stuffing rope?

good info thanks mw.. good to know, perhaps a crank breather to air cleaner would create a small draw, much like the marine ford setups.. sipping a little bit of intake charge to draw fumes from the crank case would also go a long way- however i suspect blowby is the primary cause for oil issues.. im tempted to see if its possible to machine the perkins rear seal carrier to accept a big/small block chevy or similar 2 piece rear seal - highly unlikely but ill mic the journals and see, this rope stuff seems very outdated for todays technology..
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Old 04-03-2023, 07:13   #8
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Re: perkins 4108 rear seal - isnt it just ptfe stuffing rope?

Installed the AirSep kit. Didn't help with the leaking seal.
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Old 04-03-2023, 07:40   #9
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Re: perkins 4108 rear seal - isnt it just ptfe stuffing rope?

Strangely, my 1985 4-108 never leaked a drop. No upgrade etc.
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Old 04-03-2023, 13:25   #10
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perkins 4108 rear seal - isnt it just ptfe stuffing rope?

Quote:
Originally Posted by fstarocka View Post
well im based in the US, surely i dont have to order something so basic from abroad. Seller here wants $120!! unbelievable imo, esp since its just a readily available material..


These guys in Florida have what you need. [ATTACH]
Heavydutykits.com
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Old 04-03-2023, 15:17   #11
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Re: perkins 4108 rear seal - isnt it just ptfe stuffing rope?

Quote:
Originally Posted by fstarocka View Post
good info thanks mw.. good to know, perhaps a crank breather to air cleaner would create a small draw, much like the marine ford setups.. sipping a little bit of intake charge to draw fumes from the crank case would also go a long way- however i suspect blowby is the primary cause for oil issues.. im tempted to see if its possible to machine the perkins rear seal carrier to accept a big/small block chevy or similar 2 piece rear seal - highly unlikely but ill mic the journals and see, this rope stuff seems very outdated for todays technology..
You would have to deal with the spiral groove of the oil slinger. Just an example of the finest British 1930's tractor technology on a three main crank. It's supposed to leak. Keeps it from rusting.
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Old 04-03-2023, 16:35   #12
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Re: perkins 4108 rear seal - isnt it just ptfe stuffing rope?

Quote:
Originally Posted by fstarocka View Post
Rebuilding a 4108 and curious about the "magical" rear main seal fix, looks just like ptfe stuffing box packing!

Can someone prove me wrong or right?

and what size? 1/4"? i have everything apart at my shop - might check measure the original rope seal and match some ptfe packing-
Check with your local farm tractor parts dealer they were used on the old masey 130's and similar tractors so parts are usually a lot cheaper that way.
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Old 04-03-2023, 17:22   #13
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Re: perkins 4108 rear seal - isnt it just ptfe stuffing rope?

My mechanic and I reacted similarly when we received the new seal during our rebuild....but it's a Perkins. But as one of the most reliable and generally well regarded of the old diesels, aint it great that there are still plenty of parts readily available for them?
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Old 04-03-2023, 18:07   #14
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Re: perkins 4108 rear seal - isnt it just ptfe stuffing rope?

Quote:
Originally Posted by fstarocka View Post
good info thanks mw.. good to know, perhaps a crank breather to air cleaner would create a small draw, much like the marine ford setups.. sipping a little bit of intake charge to draw fumes from the crank case would also go a long way- however i suspect blowby is the primary cause for oil issues.. im tempted to see if its possible to machine the perkins rear seal carrier to accept a big/small block chevy or similar 2 piece rear seal - highly unlikely but ill mic the journals and see, this rope stuff seems very outdated for todays technology..
Iíve also order from Parts4engines to very remote locations without issue and just as fast and faster as ordering from lower 48 or Canada. The breather off the valve cover to the air intake will provide enough draw to reduce crank case pressure but you need to install a better air filter than stock. Google ĎPerkins 4108 k&n air filterí and youíll come up with the k&n model cone filter and a cheap rubber couple and you come up with the $500 airsep kit for around $50. The filter reduces the air flow enough to draw some air off the breather, without, it just draws in air normally. This also helps reduce your engine ingesting belt dust and anything else that might be floating around your engine compartment. Watch out machining the crank, canít remember the name of the process but highly specialized and very difficult to get a new one. That new type seal from the Uk will be in your hands before you know it.
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Old 05-03-2023, 02:45   #15
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Re: perkins 4108 rear seal - isnt it just ptfe stuffing rope?

Tad is also a good us source for perkins parts in the states

https://www.tadiesels.com/parts.html

The rear main seal leaks for a reason... it’s an indicator of the oil level. If it stops leaking, it means you need to add more oil.
Love my 4108, even with the leaking rear main seal
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