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Old 01-29-2011, 06:49 AM   #1
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Arrow ISC 350 HP - Oil Breather Slobber Tube Issue

Since leaving CA and driving to Alaska and back last year, I have had an issue with my Cummins oil breather tube in that when pulling long grades, there is a significant amount of oil that is pushed out the slobber tube. It coats the engine, coach and the trailer that I am hauling. It only appears to happen when pulling grades. there was one stretch of highway in BC with a lot steep grades where I lost 1 1/2 gallons of oil out through the slobber tube.

I stopped at the NW Cummins shop in Coburg, OR on our way back from Alaska to have them check as to why this was happening. They performed two different Blow-by tests both of which fell well within the standard spec's for the engine. One test was the standard Blow-by and the other was with a full load on the engine.

I am now in the Rocky Mountain Cummins shop in El Paso, TX where I had some coach work done and after explaining to them what has been happening, they suggested to replace the original oil breather fixture with an upgraded kit, $400, that allows the oil to drain back into the crankcase quicker so it won't buildup inside the oil breather fixture and then blow out the slobber tube. They also installed an extra long slobber tube that ends just below my signature Monaco mudflap.

Has anyone experienced the same issue with their Cummins engine and how was it resolved successfully?

if this upgraded kit does resolve my issue, I am wondering why the NW Cummins shop didn't suggest replacing it last October when I had stopped to have them look at the engine then? Instead they spent almost $500 of my money testing the Blow-by only telling me that the engine has very low blow-by numbers putting it well within spec's, then sent me on my way home. I would have been better off if they had suggested spending that money towards the installation of this upgraded oil breather kit back then.

Dr4Film ----- Richard.
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Old 01-29-2011, 07:11 AM   #2
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The only times I've had issues with oil and the breather tube were catastrophic. This series of ISC had a problem with excessive blue silicone gasket material and oil sprayers on main bearings. Apparently some tech back at Cummins got carried away with the gasket making material and some found its way into the oil sprayers. When level, cylinder slap would keep the liner lubed.....when going up hill, the cylinder would run dry because the oil sprayer was plugged. I lost #6 cylinder (cracked rings, cracked piston) and when it fired it pressurized the crankcase and forced oil out through the breather tube coating everything in sight. But only under heavy load when going up a mountain. When idling, nothing came out of the breather tube.

The other time, my oil cooler (which has a lot of bolts holding the faceplate on) had a couple of bolts come loose, allowing the gasket to leak oil down the breather tube. This coated the hydraulic tank for the power steering and the radiator fan, the hoses for the HWH system and the rear of the coach and toad. But not a lot....just a steady drip over time.

I hope you don't have either of these issues. They are the only times I've had oil come out of the breather tube (or off the breather tube) in quantities large enough to coat the outside of the coach. No other issues with the breather tube and excessive oil.

Good luck with finding the cause and I hope it's minor.
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Old 01-29-2011, 07:49 AM   #3
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I had the same problem with an isc 315 in a diplomat. I put an extension on the breather tube to down below the radiator and cac.
you need to check and be sure the radiator and cac or not all dirty from the oil being blown out the breather. It sounds like a good cleaning of those parts are in order. Also another idea I have heard of is to fit a plastic soda bottle on the end of the breather to catch that blow by.
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Old 01-29-2011, 06:27 PM   #4
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I have the same problem. I got a one gallon plastic jug. Stuffed it with steel wool pads. Put the end of the slobber tube into the jug (about 1/4 of the way in. Plastic wire tied it to the frame. This is a cheap solution that works. I empty the jug once a year, when I change the engine oil.
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Old 01-29-2011, 07:43 PM   #5
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Can you post any pics of this slobber tube and it's location? My 8.3 ISC hasn't used any oil between changes but I'm curious what this thing looks like and where it's at.
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Old 01-29-2011, 08:00 PM   #6
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Snowman.........typically the slobber tube is is on the driver's side of the engine near the rear of the oil pan. It normally terminates right at the bottom of the oil pan. Hope this helpw you
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Old 01-29-2011, 08:32 PM   #7
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A word of caution re putting plastic containers on the end of the slobber tube. The tube must be able to breathe to some degree. If you use a container bottle, I strongly suggest you allow space around the tube and the container inlet or ensure several holes are in it near the top. Failure to do so can cause major smoke and oil loss at idle as back pressure builds in the motor....and this pressure needs to find a way out. Although you will kill all mosquitoes within 200 yards and lubricate your driveway, this condition does no good for your motorhome. Do not ask me how I know this!
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Old 01-29-2011, 08:43 PM   #8
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One other thought re your situation. Putting a container on the end of the tube does not really resolve the concern. Dumb question....have you checked your oil level OR the accuracy of the dip stick? Perhaps you have an overfill condition that would not be apparent if the dipstick were improperly mounted....I have heard that this is not uncommon on diesels. If this proves OK, I would then look for a condition that is allowing too much pressure to build inside the engine. Not sure what might do that, however I would look for a possible emissions-related cause. My ICS (built for California standards) does have an emission system on it, which may have accounted for the experience I mentioned in my previous post. Maybe a conversation with the local Cummins Service Manager and one of his techs would help....along with a hot cup of coffee for each. Please let us know if you find out something.....
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Old 01-30-2011, 06:11 AM   #9
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To answer other poster's question & concerns, It's not blow-by caused by any cylinder problem, nor hydraulic leaks. The oil dip-stick was calibrated and checked to make sure it was reading the oil level accurately and the crankcase was NOT overfilled. I did install a large collection bottle at the end of an extension hose with plenty of air holes in the top lid for the engine to breathe however for the last 1200 miles or so pulling grades out of CA over to Las Vegas, later over to Laughlin, and finally down to El Paso, TX, there was still enough oil coming out from someplace to splatter the rear end of the coach and all over the trailer.

Yesterday, after leaving the Cummins shop in El Paso, I had to climb a large steep grade going up over the Guadalupe Mountains between El Paso and Carlsbad, NM. So far, I am a "Happy Camper" . There was not one little drop of oil nowhere to be found, well except for maybe one little one on the end of the very long slobber tube they installed onto the upgraded Oil Breather Kit. So with the latest "Fix" that the Cummins shop in El Paso recommended and did for me, it appears to have fixed my problem. I have another 1600 miles or so to finish driving over to Florida. I will wait to see what happens after that entire trip. However, I am not sure how many long hard uphill grades I will have to pull between here and there on the I-10 freeway.

The real "Test" will be on my return trip to Alaska next year when I travel through the Rockies both in the US and Canada along with all of the grades I had traveled in BC, Yukon and Alaska.

Bottom-line, if you are having similar problems with extreme amounts of excess oil coming out of your oil breather tube, see your Cummins dealer for installation of this upgraded kit. This new fixture has a very large oblong cutout on the inside which allows for the oil to drain back into the crankcase quicker, a larger drain tube which is attached to the Turbo drain tube that goes back to your crankcase, a perforated plate where the excess air pressure is allowed to escape down the slobber tube and there is no longer any fine mesh screen which covered the entire area on the inside. I did NOT re-install the collection bottle based on the recommendation of the Cummins shop supervisor. The cost was about $180 plus installation. It took them about 2 hours or less to install.

Dr4Film ----- Richard.
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Old 01-30-2011, 07:45 AM   #10
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Hi heapbigengin,
Not to worry. The bottle has plenty of openings for the slobber tube to vent.
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Old 01-30-2011, 11:07 PM   #11
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Hey Dr4Film.....

VERY interesting re the upgraded oil breather kit. I will definitely save your messge and consider having this kit installed this Spring.
The price sure seems reasonable. Hope your problem is now history....sure sounds like it. Take care....
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Old 03-25-2011, 02:51 PM   #12
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That breather needs to vent. Don't do otherwise. And make sure if you have a hose there is no low spot in it. If you live in a cold climate any fluids in the low spot can freeze and then you will have a worse problem than what you started with.
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Old 05-05-2011, 08:13 PM   #13
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The ISC, ISL both have a form of a crankcase fumes oil separator. It is located behind the oil filter and should have a small plastic tube attached. One problem with the placement of this separator is that it is too low in the block skirt and has more liquid oil to separate out than it can handle under some conditions. Cummins Rocky Mountain is talking about applying a Fleetguard Open Crankcase Ventilator that attaches to the existing tube. It is a kit of the separator and the hoses and clamps attaching the OCV is the challenge in that the only mounting bracket we made was for one specific location. That is what you get with young engineers who have no experience in the field. I digress. I have some pictures on how that OCV can be installed. It is not difficult once you remove the lube oil filter so you can access the tube. contact me at: gary.a.spires@cummins.com
Gary Spires, Field Service Engineer for Cummins Filtration/Fleetguard
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Old 05-06-2011, 12:24 PM   #14
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just got home from az and noticed my motorcycle on the back of my 2000 mountain aire w/isc350, was covered in oil.when i checked it out i could see that the spray of oil seemed to be in line with the breather tube and there was some wet oil at the bottom of the tube. thanks for all you comments as i now need to figure out the best solution--thanks--doc
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