My port engine drive oil pressure was down. (DD 8V-71 Allison Direct Drive)Checked the level and it was on ADD.Oil looked normal at that point.Added about a quart and brought it up to full.After running engine at idle, rechecked oil and now it seems milky and bubbly.What had me looking in the first place was what seemed like drive slip.Engine was operating at normal RPM say 2000 and power from port engine didn't seem to get to the prop.I shut down the Port Engine out of caution. After about 15 minutes, fired it up and everything seemed normal, just a tad lower on the Drive Oil pressure gauge for port.Anyone have any ideas on what is letting Water? Into the drive, if that is the case?Sounds like something expensive.Hoping this is an inexpensive repair, but I’m a realist.
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Thread: Milky drive oil
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11-15-2018 09:35 AM #1Senior Member
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Milky drive oil
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Re: Milky drive oil
On my boat (DD6-92TA, Twin Disc transmissions) this was caused by a leaking transmission cooler. This is part of the combined fuel and transmission cooler and is found on the raw water side on one side of the engine. Four hoses go to it. I spent a lot of time trying to repair mine but once they start to leak the tubes inside are shot. Replace it. If one engine's is bad the other one can't be far behind.
Flush the fluid from the transmission several times, especially if in salt water.
It is hard to understand how raw water can get into the transmission against drive pressure. On my Twin Disc transmissions there is no pressure in idle while the raw water pressure is at least a few pounds, probably 10 psi or so, apparently enough to do this.Jim Grove, Fanfare 1966 50MY Hull #22 (Delivered Jan. 7, 1966)
"LIFE IS JUST ONE DAMNED THING AFTER ANOTHER." Frank Ward O'Malley, Journalist, Playwright 1875-1932
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Re: Milky drive oil
Slip is typically caused by low oil level as well as air getting sucked in by the pump. A common cause of an air leak is at the screen gasket (triangular if I remember correctly )
Oil level need to be checked with the engine running at idle not stopped. Unless you have marked the dipstick to be able to read with engine off.
Are you sure it is milky or is it just bubbles?Pascal
Miami, FL
1970 53 MY #325 Cummins 6CTAs
2014 26' gaff rigged sloop
2007 Sandbarhopper 13
12' Westphal Cat boat
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11-15-2018 03:39 PM #4Senior Member
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Re: Milky drive oil
If there is enough water in the drive oil it will be really white. Mine was also the consistency and appearance of white toothpaste.
You might run it a bit at, say, 1,200 rpm in neutral to see if the white gets worse. I wouldn't run it in gear because it wouldn't lube the transmission well. I would speculate that the mixture of water and oil should have some protective ability. However, it is not good and I would flush it out as quickly as possible as it will damage the bearings if it is indeed water.
The old way to test for water in oil was to put a spoonful onto a medium-hot skillet. Water will sizzle. But not too hot--oil will burn. Your Detroit Diesel dealer may have a better test.Jim Grove, Fanfare 1966 50MY Hull #22 (Delivered Jan. 7, 1966)
"LIFE IS JUST ONE DAMNED THING AFTER ANOTHER." Frank Ward O'Malley, Journalist, Playwright 1875-1932
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Re: Milky drive oil
Until the transmission gets nice and warm there will be bubbles on the dipstick. You could actually look milky but yet it’s just microscopic bubbles. Let it run for a little while and get really nice and toasty then check it. X2 on checking your transmission oil when it’s running.
SEVEN
1979 53' MY Hull #563
Antioch, California
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Re: Milky drive oil
If it was fine before adding oil, then its not water, its air. You're level is not right. Too high or too low will create bubbles.
Sky Cheney
1985 53EDMY, Hull #CN759, "Rebecca"
ELYC on White Lake--Montague, MI
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11-16-2018 08:00 AM #8
Re: Milky drive oil
1977 Hatteras 58' MY, Hull No. 304, 4-stateroom galley up model with 8V71TIs in Knoxville, Tennessee
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11-16-2018 12:51 PM #9
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Re: Milky drive oil
Because different installations have different amounts of fluid for coolers and filters etc. The transmission manufacturer doesn't know where the oil level and total fill will end up until the whole thing is put together. All they know is how much oil the transmission needs in it while running at temperature to function properly.
--- The poster formerly known as Scrod ---
I want to live in Theory, everything works there.
1970 36C375