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CBrucie · 05-17-2021, 05:43 PM

Hello,
I have a ISL 400 hp Cummins Turbo diesel. Noticed a plug was missing when i saw an oil spot underneath my rig. Plug looks to be between 3/4 in to 7/8 in diameter. Checked engine oil level and transmission fluid level. Both okay.
The part with the missing plug is attached to the part in the next picture. Don’t know if this an engine, transmission, drive train, ABS, or other issue. Plan to visit some diesel repair shops tomorrow to find the correct plug. Please help me identify what this is and does it need to be refilled.
Thank you,
Craig

Skip426 · 05-17-2021, 05:50 PM

The hole should be open , the bellhousing for the transmission has several applications and for some it would be plugged .

Pretty much normal to see dampness around , the hole , if there are black drips you have a rear main engine seal leak , red drips trans torque converter seal .

CBrucie · 05-17-2021, 07:04 PM

Quote:

Originally Posted by Skip426

The hole should be open , the bellhousing for the transmission has several applications and for some it would be plugged .

Pretty much normal to see dampness around , the hole , if there are black drips you have a rear main engine seal leak , red drips trans torque converter seal .

Thank you. Looks like black drips. Moved it in January in very cold weather after setting for two months. Noticed drips then, but thought it was from leveling jacks. Drove it for the first time today since then to exercise it. Went about 30 miles. No noticeable drop in oil level. Single drip today. About 110k miles on the rig. Would you recommend something like Bar’s Leaks rear main seal repair additive to see if this fixes the problem?
Thanks,
Craig

Skip426 · 05-17-2021, 07:17 PM

Not really a fan of engine oil additives , with some heat and use the seal may reset and cut the loss down . I've replaced a couple of rear main seals in Cummins / Dodge trucks and would wait a LONG time before going the replacement route in a diesel pusher.

mackwrench · 05-17-2021, 07:32 PM

Skip is correct....that "leak" would have to get a lot worse before it got better. I also am no fan of snake oils that claim to "fix" seals and leaks.

Your not missing anything, although sometimes There's a plastic plug threaded into the hole. This "hole" is strictly a access point, some engines may use a tach or crank position sensor there, it depends on what application is.

My wag is it's not the rear main seal, there's a few places it'll seep that'll cause some people to suspect the seal.

Take a few cans of brake cleaner, spray the area off as well as possible, run it at high idle for a bit in the driveway and see....

Look up around rocker cover as well, a leak up higher can seep down into flywheel housing

CBrucie · 05-17-2021, 07:33 PM

Quote:

Originally Posted by Skip426

Not really a fan of engine oil additives , with some heat and use the seal may reset and cut the loss down . I've replaced a couple of rear main seals in Cummins / Dodge trucks and would wait a LONG time before going the replacement route in a diesel pusher.

Hope using it again frequently will reset the seal. That’s some good news. Did not want to move it in January, but had to. Can’t imagine the cost of replacement and amount of downtime involved. Thank you for the advice

CBrucie · 05-17-2021, 07:46 PM

Quote:

Originally Posted by mackwrench

Skip is correct....that "leak" would have to get a lot worse before it got better. I also am no fan of snake oils that claim to "fix" seals and leaks.

Your not missing anything, although sometimes There's a plastic plug threaded into the hole. This "hole" is strictly a access point, some engines may use a tach or crank position sensor there, it depends on what application is.

My wag is it's not the rear main seal, there's a few places it'll seep that'll cause some people to suspect the seal.

Take a few cans of brake cleaner, spray the area off as well as possible, run it at high idle for a bit in the driveway and see....

Look up around rocker cover as well, a leak up higher can seep down into flywheel housing

Thank you. Will do. As you know, trying to poke around and see anything in the engine compartment of a dp is a nightmare.

Old Scout · 05-17-2021, 07:57 PM

Suspect if you stick your finger inside this "vent" hole, engine off of course, you will not find any "oil" inside the bell housing, so this is not a seal leak....what you might find is that your fuel lift pump [above the starter] is leaking fuel down the side of the engine block, picking up dirt and grime along the way, and ending up on the outside of the bell housing, near the vent hole. If you have the older CAPS fuel system on your ISL, a leaking lift pump can be a serious issue for your injector pump....

CBrucie · 05-18-2021, 09:38 AM

Quote:

Originally Posted by Old Scout

Suspect if you stick your finger inside this "vent" hole, engine off of course, you will not find any "oil" inside the bell housing, so this is not a seal leak....what you might find is that your fuel lift pump [above the starter] is leaking fuel down the side of the engine block, picking up dirt and grime along the way, and ending up on the outside of the bell housing, near the vent hole. If you have the older CAPS fuel system on your ISL, a leaking lift pump can be a serious issue for your injector pump....

Thank you. No hint of diesel fuel.

Old Scout · 05-18-2021, 10:39 AM

I know but--by the time the diesel runs down the side of the block and picks-up some dirt and grime--it looks a lot like engine oil? Did you check the under side of the lift pump?

groveln · 05-18-2021, 03:28 PM

Boy Old Scout you nailed the leaking Lift Pump dripping down & collecting dirt & looking like oil when it gets to the bottom of the bellhousing. I looked up & saw a nice clear fuel drop hanging at the bottom of the lift pump. I when up top side & all three 11mm bolts holding the pump motor to the fuel line housing took a few turns to tighten then up to spec. I'll be changing over to the Fass Titanium Signature system very soon.

Old Scout · 05-18-2021, 04:18 PM

FASS pump is probably a good solution--the three pump manifold bolts will eventually loosen and starting leaking again....new gasket or lift pump is the only longer term solution, besides the FASS pump system....assume you will bypass the OEM lift pump manifold when you install the FASS?

groveln · 05-18-2021, 05:07 PM

Yes definitely bypassing the OEM pump..I just needed to buy some time for a short trip in the coach & have considered just replacing the gasket but see on this site Cummins no longer offers it. My coach has 54k on the clock & I'm aware of the know complete pump CAPS lift pump failures over time. I do run Power Service Diesel in my fuel & have had great results over time. We know the big benefits of the Fass System & I don't want to do a service call while on the road. So I will attack the Fass system when I return.

CBrucie · 05-19-2021, 11:37 AM

Quote:

Originally Posted by mackwrench

Skip is correct....that "leak" would have to get a lot worse before it got better. I also am no fan of snake oils that claim to "fix" seals and leaks.

My wag is it's not the rear main seal, there's a few places it'll seep that'll cause some people to suspect the seal.

Look up around rocker cover as well, a leak up higher can seep down into flywheel housing

Poked around the engine compartment some more. Found leaks or seeps higher up. First picture is from rear of rig. Last two pictures taken from the access compartment inside the coach.
Does this need to be repaired? Or is this leak something I can live with?