Ok, but isn't the oil cooler raw water cooled? And if so the oil would get milky, not really black correct?
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Ok, but isn't the oil cooler raw water cooled? And if so the oil would get milky, not really black correct?
Transmission oil cooled by seawater. Engine Oil cooled by freshwater.
But still, why would that make the oil black? Wouldn't it make it milky?
Fresh or salt, whatever kind of water turns oil milky. This can also give the oil the consistency and appearance of toothpaste. I don't know what this may do to the flow rate of the oil pump but I'm pretty sure it's not good.
A bad rear engine seal will give you sooty oil on an M20. I went through this drill last year and had major transmission damage requiring a rebuild at Arcadian in Louisiana.
Did the sooty oil cause the damage? If so, what happened? Or was the cost to remove and replace the engine seal?
I would expect that the engine oil filter would remove most of the damaging grit in normal operation. Bearings in the engine are about the same as those in the transmission. Water from combustion would be bad, but my old Allisons ran about as hot as the engines so should be boiled off through evaporation. Acids on the bearings (especially the roller bearings) could do harm but the transmission oil is the same 40 weight as engine oil and so well buffered against this, as well as there being a lot of otherwise clean oil in the transmission to dilute.
Of course,once you get the transmission separated from the engine you might as well do the whole thing and be good for another 20 years.
My rear main seals leaked into the transmissions on both engines for 20 years and a lot of hard running. Never had a problem. I rebuilt the engines in 2002 and haven't leaked a drop (into the trans) since. I've got the MH gears tho.
IMHO reguarding transmission failures I see a lot of people move the clutches from forward to reverse and back without stopping in neutral to slow the shafts that's a lot of mass to change direction and hard on the transmission.
I doubt the oil leak and dirty oil caused my transmission failure. That being said, the transmission oil filter is totally incapable of removing the engine soot from the transmission once it leaks in. Early on, I changed the oil and filters multiple times and, just like the engine, with a leaking seal it was 'dirty' in no time. With a good seals, the tranmission oil looks brand new for years.
You can learn much about your transmission by checking the strainer (for metal and clutch material) and cutting open your used oil filters. Mine was full of metal leading to a big overhaul. Again, I don't know if I can blame the bad oil seal but my other transmission has perfect looking oil and no metal in the strainer or filter...