Cummins 6BTA Oil level and Crankcase Overflow

[horseschu]

I am having some oil show up in the bilge. I am suspicious that it is from the crankcase overflow. So happens, i ran into the following post on Face Book. Anyone having this issue?

Killing with kindness…. In 1985 when the Cummins B Series marine applications were first being planned, basic installation perimeters were established which included a maximum front up installation angle of 15 degrees. Maximum oil pan capacity of B Series was 14.2 Liters (15 U.S Quarts) with the standard reversible steel stamped oil pan option. Pretty much as soon as the product was launched there were requests for an alternative low profile alloy oil pan better suited to marine environments, however the low volume of marine engines could never cover the cost of developing a unique low profile oil pan. The bus industry folks came riding to the rescue as they also required a low profile oil pan to install the B Series in rear engined T drive buses and a Bus OEM was asked what required to achieve an acceptable departure angle in an 11 meter bus chassis and in response Cummins Application engineering created an 8.9 inch low profile alloy oil pan as an alternative to the 12.4 inch deep steel oil pan. The marine group had no input into the design of the low profile oil pan, but being the only kid on the block it was accepted, however when tested with 14.2 litres of lube oil at an installation angle 15 degrees engines breathed like old steam engines. Remember ‘breathing’ is NOT blowby, many folks don’t understand the difference! Work to make the 8.9 inch deep pan involved two different designs of baffle plate and three designs of oil pick up pipe in order to suppress the amount of crankcase activity, there are no less than 7 different low profile oil pan part #’s..
B Series marine ratings were originally 2,600 rpm and with a shallow low profile oil pan the engines were very active when it came to crankcase activity, however with closed crankcase control the breathing was just acceptable.. However rating development never stands still and CPL 970 the 300B was released around 1987 and in order to keep peak cylinder pressures within corporate limits the rated rpm was lifted to 2,800 rpm. Well that extra 200 rpm simply whipped a storm, with no more oil pick up modifications available Cummins altered the installation guidelines reducing maximum front up installation angle to 13.5 degrees which was a kind of sticking plaster until the advent of the 370B with a rated speed of 3,000 rpm. With 14.2 litres in the pan #6 rod is so darn close to the lube level at 3,000 rpm it whips up an absolute storm in the crankcase!
After I retired from Cummins I was purchasing B315s from Cummins Diesel which had been operating in North Sea wind farm safety vessels, the operator was changing engines out around 5/6K hours and replacing with new B315s. We were pulling the engines, flex honing, new rings, polishing cranks, new bearings, dyno testing followed by a re-paint in Diamond White and out the door, I had an order book stretching six months out, then I sold a pair of engines into a classic British Fairy boat actually owned by a friend, engines installed and the boat went like smoke, life was good! Then I had a report that both engines were suffering from low oil pressure, the resulting investigation into the cause took me three months of work. #1 the installation angle was 15 degrees, in fact one engine was 15 1/2 degrees. Oil sample showed that lube oil had gone into shear at less than 50 hours, main bearings were down to the copper and crank damaged, the rotors in the lube pump showed signs of distress, what was happening to an engine with just over 5,000 hours and showing zero abnormal wear before it was rebuilt? Digging back through old Cummins service topics I spotted the change in installation angle which prompted me to set up a low profile oil pan in a test rig and at 15 degrees the rod is almost touching the lube oil level, at 15 1/2 degrees the rod is immersed! Having a dyno I increased the lube oil level to simulate the windage seen when installation angle was increased.. At 2,800 rpm the windage creates a total storm in the pan turning the lubricant into a milkshake consistency, the flat plate oil cooler design see pic, cannot cope with the aerated lubricant, the bubbles stick to the plates becoming an effective insulator, the oil cooler ceases to operate and lube oil temperature rises until it reaches 128 degrees C at which point the lubricant is wrecked as it’s in shear and bearing failure quickly follows.
Having sold a pair of engines to a good friend in an installation which could never work I had my back to the wall! Discussing the issue with old work acquaintances I discovered that a B Series will still operate at a minimum of 10.5 litres in the pan and the additive pack in lubricant is robust enough to still cope with 250 hour oil drain intervals. We rebuilt the engines, adopted the less is best lubrication regime and the engines lived happily EVEN at a 15 degree installation angle..
Subsequently I rammed home the less is best message and always attached temperature strips to the oil pan before shipping rebuilt engines. Several years ago I noticed the Tony Athens of Seaboard Marine publishing similar advice on the danger of over filling Cummins engines, I am not a lone voice.. Always make certain your engines have properly calibrated dipsticks and never be too keen to over fill them, let them stay low, or you are killing them with kindness. See less

[MerryKate]

Horseschu - what engine do you have and in what configuration (v-drive or straight)? How much oil do you fill? Is you crankcase breather open or plumbed into intake via an airsep or similar?

What you quote is true, at least for the old 5.9 B's. I keep my 6BTA 250 oil fill at 13-14 qts, right at the bottom of the 'low' dipstick mark. Much more and oil begins to wind up in the turbo intake. My installation is a motor-box 28TE v-drive.

First thing is to check carefully all around the engine for leaks. It can be hard to see everywhere but take your time and use a phone camera or mirrors, etc.