Milky oil

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sailorbob
Posts: 41
Joined: Tue Mar 09, 2010 5:55 pm

Milky oil

Post by sailorbob »

We change the oil on Second Wind, hull 301, every fall, just before hauling it out for the winter, so that there is fresh, clean oil in the engine all winter. This year, the oil we pulled out was a little milky. This happened to us after changing the oil at the end of our first year (2005), but in subsequent years the oil was black. Now it's milky again, though not as white as it was our first year. Mid-season it's hard to tell what color the oil is without pumping it out, since the dipstick is gray plastic.

I believe that milky oil is a symptom of water in the oil. Correct? What would explain that? Wouldn't the only liquid that could come in contact with engine oil via a bad head gasket (or whatever else) be engine antifreeze (Dex-Cool)? The engine runs fine, and I pulled four quarts of oil out at the end of the season, the same quantity I put in. Though engine exhaust is a little hard to see from the cockpit, it doesn't appear white. Would a leaking raw water pump let water mix with the oil?

I'm trying to find out if this is a serious condition, and what to do next. Assuming the engine hour meter is accurate, we had 203.6 hours on the diesel at the end of 2010 (when we changed the oil at the end of last season) and 239.8 hours as we changed the oil a couple of weeks ago (only 36.2 hours for the season). That's not many hours for seven seasons.

Thanks to our fellow 350 owners for whatever input you all can provide.

Bob
Second Wind #301
wolfe10
Posts: 587
Joined: Mon Dec 11, 2006 2:58 pm
Location: Ft Myers Florida

Re: Milky oil

Post by wolfe10 »

Bob,

Yes, milky color indicates water in the oil.

Has there been a change in coolant level over the last year? Only reasonable to evaluate if the ambient temperature is about what it was when last checked. Said another way, level WILL be lower if it is colder out.

Can water get in from the raw water system-- yes, but is should not. Have you done the factory refit on the raw water exhaust with the anti-siphon valve (or is your boat new enough that it was fit from the factory)?

Have you ever cranked and cranked the engine with the thru hull open?

Either of the last two can get raw water into the engine.

Brett
Brett Wolfe
C350 #180
"Vindaloo"
Ft Myers FL
sailorbob
Posts: 41
Joined: Tue Mar 09, 2010 5:55 pm

Re: Milky oil

Post by sailorbob »

Brett, thanks for replying so quickly.

Answers - no, I have never had to crank the engine for long periods of time, at least not near the 30 seconds the manual warns about. And I have not had the siphon break upgrade work done, though I have the box of parts Catalina sent. My dealer did not believe it was critical in areas like mine (Lake Michigan), without tides or strong currents (like rivers). Maybe I need to do it anyway.

Coolant level in the expansion tank has always been an issue. We have a little Dex-Cool in the engine bilge during the season (maybe a tablespoon, which I mop up, but it comes back), and after we haul and it gets colder that amount increases, maybe a half cup to a cup. My dealer thought that was not critical - just seals shrinking with the cold. I replaced the tube to the expansion tank this summer, but the level in the tank never seems to rise as heated coolant expands. Even right after the engine has run for several hours, the tube is not full of coolant. I thought maybe I needed a new "radiator" cap, but have not replaced it yet.

This forum includes other owners talking about rebuilding the raw water pump. Could water infiltrate that way? I'm looking for diagnostic tips - I'm not a diesel mechanic! Any way to tell if this is a minor issue, with a little water getting in once in a blue moon, or a major issue with water getting in all the time?

Thanks again.

Bob
wolfe10
Posts: 587
Joined: Mon Dec 11, 2006 2:58 pm
Location: Ft Myers Florida

Re: Milky oil

Post by wolfe10 »

Bob,

I would definitely follow Catalina's recommendations and have the anti-siphon valves/new hose routing installed. Tides and current have almost nothing to do with the need for this modification. Following seas DO. And you will have those on Lake Michigan as well as off shore. Basically, without a siphon break if water level at the exhaust port (starboard aft) is higher than the engine manifold, water will flow into the engine. Small amounts will get water into the crankcase. Large amounts will hydro-lock the engine! Water is non compressible. You definitely don't want that in the rear-most cylinder!

If you still have some of the oil you drained, send it to any diesel engine manufacturer for analysis. I know all Caterpillar and Cummins dealers have oil sample kits. That would tell you if it was water or coolant in the oil.

Brett
Brett Wolfe
C350 #180
"Vindaloo"
Ft Myers FL
sailorbob
Posts: 41
Joined: Tue Mar 09, 2010 5:55 pm

Re: Milky oil

Post by sailorbob »

Brett, since your post back in October, I have had the siphon break work done per Catalina's instructions, also raising the muffler and inserting the thumb screw drain plug in the muffler. Unfortunately, I had dumped the drained engine oil in the recycling barrel before I saw your suggestion about getting the oil analysed. I will just have to wait for the 2012 season to see if the siphon break work keeps the oil from turning milky once again. Fingers crossed.

Bob Fine
Second Wind #301
wolfe10
Posts: 587
Joined: Mon Dec 11, 2006 2:58 pm
Location: Ft Myers Florida

Re: Milky oil

Post by wolfe10 »

Bob,

With water in the engine, the other thing you need to do is insure that all the moisture in the engine has been evaporated. You can get a quick indication if moisture damage by removing the oil filler and looking down in the head with a flashlight to see if there is any evidence of moisture.

Brett
Brett Wolfe
C350 #180
"Vindaloo"
Ft Myers FL
saileagleswings
Posts: 46
Joined: Mon Sep 10, 2007 8:46 am
Location: Punta Gorda Fl
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Re: Milky oil

Post by saileagleswings »

Coolant level never rises as engine heats up? If so, check the very small diameter passage in the neck of the coolant reservoir.

If the coolant level in the expansion tank is higher than the reservoir, coolant should flow out of the reservoir when you remove the pressure cap. If it does not, I believe the cap cannot regulate the coolant pressure when the engine heats up.
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