Oil leaking out of vent tube on a cummins 8.3 liter diesel

[Gary Hines]

Does anyone have an idea or knowlege on a 8.3 liter cummins diesel engine . Why does the oil breather leak out a gallon of oil every 40 miles? vent tube not plugged , no smoke out of engine, oil pressuer good ,no overheat.

[stink]

Maybe a few reasons, the oil separator is clogged, too much blowby past the pistons or a crack somewere. With the amount you also may have way too much oil in engine. I'm thinking the oil separator is clogged (I hope)

[CountryFit]

Originally Posted by Gary Hines

Does anyone have an idea or knowlege on a 8.3 liter cummins diesel engine . Why does the oil breather leak out a gallon of oil every 40 miles? vent tube not plugged , no smoke out of engine, oil pressuer good ,no overheat.

In the past weekend I went underneath my engine and saw the tube being wet; not seeing any oil drops on the ground though... I was wondering what the cause was.
A gallon on 40 miles appears to be A LOT. Please keep us posted what you find out.

[rvrepairnut]

Originally Posted by Gary Hines

Does anyone have an idea or knowlege on a 8.3 liter cummins diesel engine . Why does the oil breather leak out a gallon of oil every 40 miles? vent tube not plugged , no smoke out of engine, oil pressuer good ,no overheat.

IF its all coming out of the breather then u have very serious internal engine problem. The only way I know of for that huge amount of oil to be dispelled from the breather tube is ring failure.Are u having any trouble starting it? A GALLON of OIL every 40 miles is extreme to say the least

[Craig_R]

Not sure how long you have owned the coach but it may also be that the dipstick is not properly calibrated. This could cause an overfull crankcase condition that could cause the problem you are experiencing. Dipstick length is determined by the chassis manufacturer, not the engine manufacturer. I know it sounds counter intuitive but because one specific engine will fit multiple applications that's the way it is. I think this is the first thing I would explore.

Some engines were also manufactured with different oil pan capacities. It's important to determine what yours is.

Once you have determined the oil pan capacity, drain the oil and change the filter. Fill the crankcase with the specified amount of oil. Do not go by the dipstick. Start the engine and bring it to operating temperature. Shut it down and let it sit for 15-20 minutes so all oil drains back into the pan. Now look at the dipstick. Oil level should read at the high mark. If not, take a file and make a new high mark on the back side of the dipstick and a new low mark that is proportionate to the distance between the two marks on the front of the dipstick.

We had to do this on an entire nationwide fleet of International Trucks my company purchased new in 1991. They all came through with the wrong dipsticks and were overfilled to the point that oil would splash up on the sensors and generate an Overfull Crankcase Fault Code and a Check Engine Light. Of course for a few days our mechanics were getting deluged with phone calls from the road and our drivers were paranoid until we got the issue figured out.

[deandec]

Try running a ways without that extra gallon to see if there is any significant additional oil loss.

Could be overfilled as stated above.

[rvrepairnut]

Originally Posted by deandec

Try running a ways without that extra gallon to see if there is any significant additional oil loss.

Could be overfilled as stated above.

although there is some merit to what your saying.I seriously doubt a gallon of oil overfill spread out in a oil pan this large would be condusive to it spewing a gallon of oil out of the tube every 40 miles
I also dont beleive the OP 100% when he says GALLON of oil every 40 MILES and yet the unit performs flawlessly

[Craig_R]

Originally Posted by rvrepairnut

although there is some merit to what your saying.I seriously doubt a gallon of oil overfill spread out in a oil pan this large would be condusive to it spewing a gallon of oil out of the tube every 40 miles
I also dont beleive the OP 100% when he says GALLON of oil every 40 MILES and yet the unit performs flawlessly

I know I would be comparing apples to oranges here but the old 671, 6v71 and 8v71 Detroit Diesels aka "Detroit Oil Leakers" were notorious for spitting out the first two quarts of a full crankcase through the breather tube within 15 miles of being filled. I believe they had a much larger crankcase capacity than today's engines. That was why most knowledgeable DD operators just ran their engines 2 quarts low. Just sayin'...

[Mr_D]

Originally Posted by rvrepairnut

IF its all coming out of the breather then u have very serious internal engine problem. The only way I know of for that huge amount of oil to be dispelled from the breather tube is ring failure. Are u having any trouble starting it? A GALLON of OIL every 40 miles is extreme to say the least

If the crankcase isn't overfilled then I agree with the above!

Probable cause is a "dusted" engine and needs a top end rebuild.

[rvrepairnut]

Originally Posted by Mr_D

If the crankcase isn't overfilled then I agree with the above!

Probable cause is a "dusted" engine and needs a top end rebuild.

actually that will be a bottom end rebuild

[KSCRUDE]

Originally Posted by Craig_R

I know I would be comparing apples to oranges here but the old 671, 6v71 and 8v71 Detroit Diesels aka "Detroit Oil Leakers" were notorious for spitting out the first two quarts of a full crankcase through the breather tube within 15 miles of being filled. I believe they had a much larger crankcase capacity than today's engines. That was why most knowledgeable DD operators just ran their engines 2 quarts low. Just sayin'...

The old 8V71 Detroits were called a 318 for 318 HP I think. Any most said they got that name as they leaked 3 gallons a day out of 18 holes. No seriously, weather you topped them off or not, a good one would use a gallon or two a day.

[Genset]

Yep, The old trusty 8V-71 known as the 318 got a bad rap, in the old days they had stamped steel valve covers and they frequently were not reinstalled correct and yes they did leak. Then DDC came up with the aluminum casting for valve covers and great gasketing, end of leaks, then they got busy with better gasketing and seals. I know as I ran 8V-71, 12V-71 and 8V-92, they all rusted where no paint, ran 2000 miles and oil on dipstick never moved and engine was dry, yes all three were dry, sold the 8V-71 to a charter bus operator, the 12V to a well driller as his origional 12V died big time with 25k hours on it and needed new engine, so he started throwing money at me until i agreed to sell it, that is when I installed the 92 series engine, it was an origional first run, so easy rebuilt and throw it into the MCI7 where all the others had been.
No such thing as a bad DD engine, just poor mechanics. Always said you have to love a DD to get the best out of it, if your a Cummins or Cat mechanic, chances are good, you will have poor luck with em.
FWIW
Dave

[stink]

Had many years working on the old Detroits. Genset, you sold the rare 12v. I only seen one. Got to tune a 16v once!!

[Genset]

Stink
It mostly started about 40 years ago, then about 25 yr ago,it got serious when I bught a 1972 MCI7, converted it to a RV, every nut & bolt was removed over the next 15 years checking, if a part looked as good as new, it went back, if it showed wear, it got replaced, so from the wiper shaft bushings to the rear bumper, it was a total check & rebuild, every brake, gear, bearing, all stearing parts, air brake & lines as needed, every part, wound up with a new bus in old skin, spent major bucks on the unseen part of it and near zero on what you saw, a sleeper indeed.
Origional engine was the 8V, with 60 Injectors. After a total rebuild after I melted the top rings due to too much advance, had advanced timing, timing at 1.484 with the 70 Injectors, ran perfect,no smoke but the top rings could not take it, so rebuild and set timing at 1.75 I think and all happy, not as snappy HP wise but still very good, then the RTO910 gear box. ALways wanted the 12V, and after many trips measuring and checking, bought a run out core with the deep oil pan etc. Needed new crankshaft, damper, all cyl kits, all 48 exhaust valves, both blowers, new oil pump due to origional was the scanvenger double pump due to the deep pan for steep operational angles, (Bulldozer), anyway was a total rebuild back to new specs, ran like a 1st class pair of 238's. Crank was cracked, why the new damper pully.
Ran it 20+ years, every state east of the Miss River & Canada, never let me sit anywhere, very dependable and after the 1st rebuild, never used any oil on any of em. When I got too old to be able to crawl around it, fix or check things, I decided to try a store bought coach, went with the Foretravel U320 with the ISM500 Cummins all electronic, it runs so sweet and I dont have to touch it, today one of my employees does the oil changes etc.
Been a fun trip and still miss the old DD, 8V for dependability the 12V for raw torque, would spin wheels off idle in 2nd gear, amazing critter.
Now at 71, after a stroke & bypass surgery, I enjoy burning diesel fuel.
Side note, Both Fats Domino and Charlie Daniels got some education with the 12V, Fats insisted I pull over, he had to see why the large radiator on rear of the MCI bus, Charlie, bought a new bus with the DD 60 Series after his Provost 8V-92 could not run with the old junker with Va license tags in the mtns. Lots of good experiences with the 12V
Merry Christmas
Dave