Oil in coolant

Paul in Colorado

Paul in Colorado

Senior Member
I am getting ready to have the original engine in my 1930 Town Sedan rebuilt. When I drained the coolant, there was a significant quantity of oil in it. There is no coolant in the oil pan. What should I look for in the engine that might cause this?

Paul
 
How did you know? It would seem to me if a quart of oil was wrongly dumped in the radiator, wouldn't it emulsify into a creamy mess? has the engine been siting fro ma lont time and the oil settled out? thorough inspection and magaflux should be in order.
 
I know that no oil has been dumped in the radiator since the coolant (Sierra) was replaced. The car has been driven fairly regularly, the last time being about a month ago. When I drained the coolant, there was a thin layer of black oil on top of it. I would expect that a cracked block or head would allow coolant to drain into the oil pan, and I saw no evidence of that when I drained the oil. I can't picture where oil could get into the coolant, since the lower water inlet is above the pan.
 
It's a leakless water pump, and I haven't greased it since I installed it about 5 years ago. The oil is too thin for grease. A good suggestion, though.
 
I think what you have is really not oil,although it looks like it.I think it is a by-product of combustion,leaking into the water passages somewhere.I've seen a lot of it on old equipment,we call it sap.It is sometimes kind of brown,like creosote.I little bit of it looks like a lot when floating on anti-freeze.Have you ever seen what looks like oil seeping out from around a head stud? You would swear it is oil,even thought you know there is no oil up there.It is combustion product,marrying up with a little bit of some component of the anti-freeze,and the result is a black gummy oil.
 
That's an interesting thought. The engine is quite worn, and there is seepage around one spark plug and a little at the head gasket. Does the combustion product get into the coolant from a head gasket leak or a cracked head? If so, why doesn't the coolant get into the cylinders and oil pan?
 
Paul in Colorado said:
That's an interesting thought. The engine is quite worn, and there is seepage around one spark plug and a little at the head gasket. Does the combustion product get into the coolant from a head gasket leak or a cracked head? If so, why doesn't the coolant get into the cylinders and oil pan?
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Because the combustion has a lot of pressure and the coolant is non-pressurized. I think Keith has the most plausible explanation.
 
1 theory is that the combustion pressure is high enough to leak past the head gasket or through the crack but the coolant pressure is not. No coolant in the cylinder no coolant to leak past the rings into the oil.
 
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The cooling system is not pressurized,and the combustion is under a huge amount of pressure.I'm sure guys that have made a study of this,like Larry Brumfield,can tell you exactly how much PSI is generated in the explosions.Coolant may be weeping into the chambers at rest,but very little,and just gets burned on startup.I would say it is being forced through a corroded head gasket.I know of an engine in a doodlebug that is doing exactly what yours is.The owner had no clue if it would run,he is a junkie and had picked it up in a load of iron.It had a cracked head so I gave him one that needed planing.It was domed up in the middle.He freed the valves,put the head on with a used gasket,and fired it up.He has a winch on it with a boom and uses it in the yard for scrapping.If he had any idea it was any good he would have sprung for a gasket and a head shave.As it stood he didn't know if it would pound and rattle when he fired it.As it is he is pumping sap out around a couple of head studs and some into the radiator.He plans to fix it when something actually goes.He has 8-10 years on the used parts now.
 
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