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  #1  
Old 09-28-2001, 11:07 AM
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Location: Concord, MA
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Unhappy Oil in coolant

I just drained coolant for some maintenance work, and found that it is contaminated with oil. The coolant has been in there since Fall of '99 (two years), and is due for a change and flush this fall anyway.

I hate to say this, but the terrible feeling in my gut, after all of my discussions about the virtues of synthetic oil (Amsoil H.D. Diesel), is that I think the oil is getting past the head gasket. I do not have ANY symptoms of a blown head gasket....no steam from exhaust, no water/foam in oil, no performance problems, and the car does not consume oil or coolant. My estimate is that there is about one tablespoon of oil in the whole system.

I hate to say it, but I think I am about to go back to conventional oil (Rotella 15w40) and 3K mi. oil changes for a year and see how much I get in the coolant a year from now.

Does anyone have any other suggestions on what to do, or where the oil may come from. One option is to continue with synthetic oil, live with it, drain coolant & flush each year. Oil in the coolant does not help with heat exchange, but I have not noticed any tendency for the car to run hot even in 100 degree weather with AC on.

I may put in a little metamucyl or sawdust to see if I can seal things up!!!

Thanks to all
Mark

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Old 09-28-2001, 11:28 AM
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Hopefully you don't have a really bad problem considering the slow leakage. It's interesting that you have oil in the coolant but not coolant in the oil. I thought the coolant typically operated at higher pressure than what is found in the crankcase, so the natural flow would be coolant into oil. Would be interested in hearing other's thoughts about how oil gets into coolant. (Maybe during cooldown somehow?)

Not to start an oil jihad - I use Shell Rotella T dinosaur oil with STP oil treatment (said to be a synthetic additive). Oil and filter changed every 4,000 miles, a daily driver - 150 miles/day.

I hereby issue a fatwa against using synthetic motor oil in diesels.

:p

Ken
1982 300D
310K miles
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Old 09-28-2001, 01:28 PM
SW SW is offline
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Did you drain from the block or the radiator or both? If it was from the block, maybe the coolant picked up some oil/sludge from the outside of the engine while draining? I couldn't tell without seeing what the coolant looks like.
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Old 09-28-2001, 01:58 PM
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oil in coolant

I drained from the radiator....the surface of the coolant didnt just have a sheen...the surface was just about covered with droplets of oil.

Question..does anyone know if coolant can get into oil by way of the gasket on the oil filter housing....where the housing attaches to the block?

Mark
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Old 09-28-2001, 01:59 PM
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If there's only a teaspoon of oil in the coolant, and this is after two years, I don't think there is much to worry about here. Regardless where it's coming from, that's not very fast. You probably drip more oil on the road that that!

Me? I'd change the coolant, keep using the synthetic and just monitor the situation.

Definitely DO NOT put sawdust, metamucyl or anything else in the coolant besides coolant! You may plug up the tiny leak, and probably put a coating of sludge throughout the system. You might even plug the little passages in your radiator!

Relax and driver her some more until you develop a real problem. Then, repair her.

BCingU, Jim
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Old 09-28-2001, 02:44 PM
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Mark,
Oil pressure is much greater than coolant pressure! 3 bar on your oil pressure gauge is 44.1 psi and it goes higher than that (bypass valve to limit it in the 60's, I think). Coolant pressure tank cap will be rated 8-20 psi on most cars, hence oil into coolant is more common than other way around. Your other question- there is no connection with the water jacket at the gasket of the oil filter housing. In the "old days" it was common for us to retorque the heads on small block chevys we were running on street rods and "kit cars" after running them a few thousand miles. Don't know on diesels (only have had the 300SD) but maybe someone here has tried that with success, but that sounds like a "minorly leaking" head gasket as opposed to a "blown" one and maybe a "cinch down" will work. (wishful thinking)
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Old 09-28-2001, 05:33 PM
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Good point on the oil pressure being higher than the cooling system. I was thinking of the crankcase/sump minimal pressure but forgot that there has to be oil pumped up to the valve gear through the head.

Some people on other engines have had success eliminating head gasket leaks by retorquing the head bolts. Don't know whether this would work on an MB diesel or not.

As has been mentioned, you probably just want to keep an eye on the fluids for contamination and continue to drive. Maybe the next time you have the valve cover off to adjust the valves, you can retorque the head bolts. They do get torqued in a specific pattern.

Ken
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Old 09-28-2001, 06:04 PM
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I have heard of MB radiators that will get a hole in the core between the coolant part of the radiator and the transmission fluid part of the radiator. You could have spring a VERY slow leak there and what you are actually seeing is transmission fluid..

Just an cheaper alternitive..

John
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Old 09-28-2001, 08:33 PM
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You can get oil in the coolant from a bad head gasket or from a leaking transmission cooler. The head gasket is cheaper, since the transmission goes to the bad place very fast if it gets coolant in it.

Check the transmission for water pronto!

The easy, although not foolproof, way to tell the source of the oil is thus:

Head gasket leakage usually deposits very black oily gunk in the coolant, as it contains blowby and exhaust gasses. Transmission fluid is usually red-brown and may smell of transmission fluid.

Check also for excess pressure in the cooling system when the car is cold -- leaking head gaskets will fill the headspace in the coolant tank with exhaust gas, which doesn't contract enough to depressurize when cold. You can also check for exhaust gas bubbling in the coolant with the engine running and the pressure cap off -- it will bubble cold as well as hot.

I wouldn't wait a year to see -- synthetic oil will NOT cause a leak into the coolant while petroleum won't.

Peter

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