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Old 12-04-2014, 05:45 AM   #1
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An engine puzzle: Oil in coolant but no water in oil

We have twin 600685SFM Deere Engines with approximately 3,000 hours. For the past several years, the starboard engine has given up a black sludgy substance that coats the plastic coolant overflow container. Twice we have had the coolant system flushed, once as long as 7 hours. Once we pulled and replaced the coolant overflow container. Each year we conduct an oil analysis as a regular procedure on our boat. Everything in the oil analysis is nominal and has been each year. No evidence of water has ever shown up. An analysis of the sludge in the coolant container indicates that it is oil. The puzzle:

How the heck can oil get into the coolant system without any coolant or water getting into the oil system?

Thanks for any ideas!

Cheers,

Don
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Old 12-04-2014, 06:14 AM   #2
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Easy - the oil is under higher pressure than the coolant - 40-50psi vs 12psi. Is the boat in Bellingham? If so, I'd give Hatton a call down in Ballard. I'm not sure about your particular engine (is it a 6068SFM? There seem to be some extra characters in there compared to the numbering I'm familiar with) but turbo gaskets are a common problem on some engines.
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Old 12-04-2014, 07:24 AM   #3
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You also might check any installed oil cooler , where as noted oil 60psi, water 10-15psi
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Old 12-04-2014, 07:25 AM   #4
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Oil cooler? Brian Pemberton at NW Explorations may be able to steer you to a very good local JD guy. Brian knows GBs.
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Old 12-04-2014, 08:36 AM   #5
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Can someone explain to me why there is no coolant in the oil. I get that when running the oil is at a higher pressure but as soon as the engine stops the oil pressure returns to 0...while the coolant remains at pressure for quite a while.

The only theory i can come up with is that pressure required to push past whatever weakness is in the loop requires more PSI than the ~12 PSI of a cooling system. but the increased pressure of the oiling system is sufficient to force the oil into the cooling system.

I guess that theory holds water (pun very much intended) but it does sound odd that problem hasn't gotten worse.

Another thought maybe exhaust gas in the cooling system. Over time it could contaminate the coolant with oily exhaust gas...which he'd likely have at start up and as the system warms it expands enough to close whatever hole is in the system.

Does that idea have any merit?

If it were mine i'd start with a (cold) coolant system leak down test. tester is cheap and not at all labor intensive to do.
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Old 12-04-2014, 10:19 AM   #6
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Oil from the tranny cooler would be clean. You probably check tranny oil levels.
Foamy sludge sounds like exhaust. There is a test for exhaust gasses in coolant. Try a Napa store.
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Old 12-04-2014, 10:20 AM   #7
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A coolant system leak test is easy. Got to an auto parts store and see if you can rent a tester. Advanced Auto Parts has a very nice one and all they require is a deposit which is refunded when you bring it back.

Hook it up to the fill cap, pump it up to 12 psi and look and listen for leaks and watch the gauge. If the pressure drops, you have a leak whether you can see, hear it or not.

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Old 12-04-2014, 11:44 AM   #8
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He doesn't report coolant loss and oil tests are not showing coolant in oil.
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Old 12-04-2014, 11:54 AM   #9
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Originally Posted by djmarchand View Post
A coolant system leak test is easy. Got to an auto parts store and see if you can rent a tester. Advanced Auto Parts has a very nice one and all they require is a deposit which is refunded when you bring it back.

Hook it up to the fill cap, pump it up to 12 psi and look and listen for leaks and watch the gauge. If the pressure drops, you have a leak whether you can see, hear it or not.

David
I've seen it where an engine oil cooler will not start leaking until about 30+ psi. This particular application is in many cases an oddball marine HX and doesn't always reply to a coolant leak down test. Would a 12 psi test be sufficient to detect an oil cooler leak?

But I have no idea if the OP's JD has a coolant based oil cooler. On my engine the oil cooler's bigger role is to insure the oil gets up to coolant temperature when lightly loaded so oil is working its magic and volatiles are burning off.

If it were me I'd get a good JD guy involved, whether out of Seattle, Anacortes or Bellingham.
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Old 12-04-2014, 12:47 PM   #10
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IMO he needs to test for exhaust in coolant. I cant think of any way to get lube oil in coolant unless he has an engine lube oil cooler.
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Old 12-04-2014, 01:49 PM   #11
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Head gasket. Do a leakdown test.
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Old 12-04-2014, 02:16 PM   #12
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Before chasing any oil cooler, see if there is one, and whether its sea water cooled or engine coolant cooled. If you have a coolant cooled oil cooler (thats a lot of cools), then oil and coolant come together there.

The turbo is another place where they come together, and on some deere models is a common failure point, so I'd look there first.

An experienced deere mechanic will know all the common failure points and likely save you a lot of money by avoiding things like a head gasket replacement when other things are much more likely.
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Old 12-04-2014, 03:44 PM   #13
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These responses have been very informative. Thank you!!

We just had a sea trial at WOT completed and everything was pretty much normal. The mech, who knows JD engines, suggests flushing the coolant system. I am concerned since we have done this twice before in the past three years. It is not cheap. Each time the problem comes back.

Thanks, again, for any insights that you might share.

Cheers,

Don
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Old 12-04-2014, 05:53 PM   #14
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Don

Three questions:
  1. Is your turbo jacket water cooled?
  2. Do you have a jacket water cooled oil heat exchanger?
  3. Have you had your coolant analyzed - for HC products and for engine oil?
Good luck, BTW what outfit was the mechanic from?
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Old 12-04-2014, 09:52 PM   #15
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Find another mechanic. What good is flushing going to do (for the third time) if you don't solve the root cause?

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Old 12-04-2014, 10:15 PM   #16
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Quote:
Originally Posted by eseyoung View Post
Can someone explain to me why there is no coolant in the oil.
Slight leaks like this are often challenging to find especially if they are intermittent. It may leak only immediately after cold startup.


This is the time there is maximum differential pressure between oil and water. (oil up to 40 psi higher than water) When shutting the engine down the differential pressure is much lower (water 15 psi higher than oil)


Also, on startup block & heads are not yet up to temperature/fully expanded, so head gaskets may not be sealing 100%. On shutdown the coolant temp and pressure may drop faster than the engine block temperature.


One more point - Very small amounts of oil in coolant are easier to detect than the same amount of water in oil (which flashes off)
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Old 12-05-2014, 09:34 AM   #17
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Any history on this engine that suggests it has been overheated in the past? If, yes then headgasket issues or cracks in the head or cylinder liner seals/water jacket come in to play. These have been known to heal once warmed up, but eventually fail. Good luck.
There are some coolant filter applications that would trap the oil and particulate and allow some extended service of the coolant under these conditions.
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Old 12-06-2014, 09:28 AM   #18
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Sorry for the delay. Travel.

There is no history of over heating. That is a good idea about coolant filtering, PopArcher. I had not thought of that. Do you have any recommendations? Where would I find these?

Good point about water flashing off in oil, AusCan.

Answers to the three questions from sun chaser:
Is your turbo jacket water cooled?
The engine is turbocharged and does have a jacket water cooled (coolant, not sea water) turbine housing.

Do you have a jacket water cooled oil heat exchanger?
There is a heat exchanger that transfers heat from the water jacket (coolant) to the sea water. There is also a engine oil cooler that is in the jacket water.

Have you had your coolant analyzed - for HC products and for engine oil?
The oil sample indicated the present of oil and did not indicate carbon deposits.

I really appreciate the help with trying to understand this puzzle. Thank you, everyone!

There are no other symptoms to indicate a problem. the sea trial went perfect, no bubbles in the cooling system or oil present afterwards (the coolant system had been flushed and cleaned). Our next step is to run the boat to see if the problem appears again. One theory is that someone inadvertently added oil to the wrong fill point. (The boat is in charter.)

The mech is hesitant to disassemble any part of the engine to try to locate a source unless the problem increases. He does not want us to spend a large amount of money for exploratory surgery with very little hope of finding a source. If it develops, with more oil in the coolant expansion tank or some other symptom, then he would feel better with proceeding. We have full confidence in him. Very strong local reputation, especially with JD engines.

I welcome all thoughts. It is a learning journey for us. Thanks!!!

Cheers,

Don
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Old 12-06-2014, 11:12 AM   #19
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If your vessel is in charter with NWEX your "problem" is in good hands. I am familiar with their boat check list and it puts most of us to shame as to how we maintain and service our vessels.

But you have raised the problem with a charter vessel, not enough owner time to really follow these piddling things along.
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Old 12-06-2014, 03:07 PM   #20
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Coolant filter reference.

http://www.donaldson.com/en/engine/s...ary/000376.pdf

http://www.donaldson.com/en/engine/s...ary/070044.pdf

Check this info out on coolant filtering. I am not affiliated with the vendor.
I am sure they can set you up with a good system.
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