Oil in radiator...

... in my '97 Plymouth Neon Highline, AT, 2.0L 4 cyl. I immediately thought "bad head gasket" and have had a couple of other people suggest
that. But my oldest son says that would cause the *opposite* (i.e. water in the oil). He says it could be a bad water pump seal. What do you guys think?
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wrote:

Bad water pump seals lets water out. Typical Neon head gasket failure after 1995 is oil in rad. First. Can progress to oil outside the engine, antifreeze in the oil, or antifreeze outside the engine.
Not possible for oil to get in the rad from the water pump.
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On 12/31/10 2:24 PM, snipped-for-privacy@snyder.on.ca wrote:

Thanks for your input. Guess I'm looking at a bad head gasket after all.
Karl
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Given the relative pressure involved the only way I can see for oil to get into the radiator is when the system cools down and a vacuum is created in the cooling system.
The first thing I would check would be the radiator cap to make sure it will allow a back flow in the correct mannor.
The second assumption would be an oil leak building up on the engine where that oil could be vacuumed into the radiator (see above).
Which rasises the question: Is it possable someone has put oil in the radiator overflow catch basin with the intent of messing with your mind?
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On 1/1/2011 2:31 AM, NotMe wrote:

The "relative pressure" of the combustion chamber is much higher than the cooling system. It's easy to find oil in the radiator with a bad head gasket.
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wrote:

You have the cause wrong, but the effect right. Or lets just say you have it about half right. It is the fact the OIL PRESSURE is higher than the pressure in the radiator that causes oil in the radiator.There is no oil in the combustion chamber of a properly operating automotive engine. The primary gasket failure on Neons AFTER 1995 is leakage from the oil gallerey to the cooling jackets and the oil galleries to the outside of the engine. When it gets bad enough you also gat coolant in the oil. Prior to 1995, when the steel sandwich gasket was introduced,The primary failure mode was leakage of combustion gasses into the cooling system, with leakage of coolant into the combustion chamber a direct result. When running, combustion pressure was higher than cooling system pressure, but when you shut down a warm engine, the 14psi cooling system pressure was higher than the combustion chamber pressure, allowing coolant to enter the cyl.
With the new headgaskets, combustion chamber leaks are ALMOST a thing of the past
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On 1/2/2011 7:49 PM, snipped-for-privacy@snyder.on.ca wrote:

I've always found bad headgaskets because the combustion pressure forces coolant out of the overflow pressure release causing low coolant and overheating. When you go to add coolant you find the muck and residue on the cap and start-up produces white smoke from the exhaust after coolant enters the combustion chamber on after shutdown. I've rarely seen oil in the coolant because unless you have a very bad leak or make only short trips, this usually boils off after driving.
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wrote:

No, the reason you don't see oil in the coolant is because the failure you are seeing is different. You see antifreeze in the oil becuase it runs past the rings with the engine shut off and the cooling system pressurized. This is a "combustion chamber leak" and it also causes smelly white smoke on initial startup.
When the leak is from an oil pressure gallery, which is (relatively) common on the later Neon, and was common on some Toyotas, for instance, the failure does not affect the combustion chamber (at least in the beginning), it just transfers oil into the coolant, or coolant into the oil, depending on the pressure differential and the characteristics of the failed gasket and location of the failure..
In these types of failures compression gasses do not get into the coolant, overpressurizing the cooling system and blowing out coolant.
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