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327F getting water in the oil

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dcbullington

Contributing Member
This is a strange situation and believe me, I've had plenty of those with these engines! My stbd engine runs fine with no issues until the outside temp gets below 50 deg or so. Once that happens, I notice water droplets on the dipstick and a small amount of water in the bottom of the oil pan. I ran the boat over 30 hours last summer with no issues at all, but once it started cooling off, bam! I found the water. My mechanic is baffled, he thinks maybe the engine isn't warming up right when it gets cold like that (it doesn't get above 130 or so even in the hot weather unless you run it WOT for a while, but neither does the port side and there is no oil there summer or not). Any ideas on this one? Has anyone seen anything similar? Thanks, Dave
 
I'm guessing that you are stating temperature being relatively constant at 50 degrees F, as in fall weather. That means the water is colder as well.

I am going to hypostulate some things related to heat.... mostly expansion of cast parts. You may have a hairline crack in the block between the cooling jacket and the oil gallery. If the engine is running cold, then water would seep in through the crack and contaminate the oil. Usually small block chevy cracks outward, around number 4 cylinder near the deck, but it depends. Cracked blocks are VERY common on old engines in a marine situation, and because the water pressure through the cooling system is not very high, like a closed system, the crack goes unnoticed. The other problem could be a head gasket, that is leaking in one place, again, only because the engine is running cool. When engine runs a little hotter internally due to higher water temperatures, the crack or gasket seals up... at least enough to mask any small amount of water getting through.

What your temp gauge says, and what is happening inside the engine is somewhat different, since the temp gauge is the average temperature of the water running by the sending unit. Oil runs hotter, and water runs hotter, depending on where it is in the system. The thermostats on 283F and 327F are 160F if memory serves, and they may be worn out too. Having the temp gauge calibrated and restored, along with a new sending unit, is a useful exercise.

My two best guesses. Both of these are pretty hard to diagnose completely without taking the engine apart, but it is possible. You can do a leakdown pressure test of each cylinder to determine if there is a crack, but you can also get leakdown from valve seats if the engine has some hours on it. You can look very very carefully at the outside of the block to see if there is evidence of cracking on the outside but beyond that, you are committed to tearing an engine down and magnafluxing things.

If this 327 is original and has never been rebuilt... well...
What year is the boat and engine? Has it ever been rebuilt?
 
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I might have solved this if my theory proves out. I think the water is condensation getting in at both the dipstick and the oil fill cap. Neither is water tight and there was a small amount of foam in the oil fill cap itself. The rubber gasket is dried up and falling apart and the dipstick is loose as well. I will replace them and see if that fixes the problem. I ran the boat yesterday for an hour or so and didn't see an increase in volume of oil, just traces of foam on the dipstick and fill cap.
 
dcbullington said:
I might have solved this if my theory proves out. I think the water is condensation getting in at both the dipstick and the oil fill cap. Neither is water tight and there was a small amount of foam in the oil fill cap itself. The rubber gasket is dried up and falling apart and the dipstick is loose as well. I will replace them and see if that fixes the problem. I ran the boat yesterday for an hour or so and didn't see an increase in volume of oil, just traces of foam on the dipstick and fill cap.
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Ayuh,.... At what Temp does the motor run,....


Generally speakin', condensation is controlled by usin' a higher t-stat, 'n runnin' the motor at atleast 160°/ 170°....
 
Can't get them above 125 ish, have new 160 T-stats (only range I can find) and they just won't heat up, especially when it's cold outside. I suspect that you are right on target and this is why the problem is more pronounced when the ambient temp drops below 50 or so. Do you think the new t-stats are not closing all the way? I put them in 2 years back but only have about 100 hrs on them.
 
dcbullington said:
Can't get them above 125 ish, have new 160 T-stats (only range I can find) and they just won't heat up, especially when it's cold outside. I suspect that you are right on target and this is why the problem is more pronounced when the ambient temp drops below 50 or so. Do you think the new t-stats are not closing all the way? I put them in 2 years back but only have about 100 hrs on them.
Click to expand...

Ayuh,... I'd try 2 more,... Time sittin' is worst than time Runnin'....
 
I'd be inclined to check the rest of the cooling system as one or more parts may be leaking (internally) as well... they can give similar symptoms to what you describe...
 
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