1995 3100--oil in coolant

[Schurkey]

What would be the typical cause of a '95 3100 that starts and runs good, but has the overflow bottle filled with engine oil?

 

This thing runs sweet. I'm actually considering a doofus prior owner dumping a quart of oil in the radiator overflow bottle by mistake or by stupidity. Oil in the bottle looks reasonably clean. Radiator level is low, have to reach in with a stick to find coolant. No smoke or steam out the tailpipe. No milkshake oil after a short drive, and the oil is amber, not the reddish hue of the trans fluid.

 

In short, no obvious evidence of coolant in the oil or in the cylinders, but plenty of engine oil in the overflow bottle. Odometer of this Lumina shows 275k miles, but I have no service history--the engine could have been replaced.

[Galaxie500XL]

Short of the prior owner having actually poured oil into the overflow, very few things cause oil to appear in coolant, other than a headgasket failure, or, if I'm remembering correctly, bad lower intake gaskets can possibly lead to oil in the coolant. I'd clean out the bottle, refill with coolant, then watch the coolant level carefully

[RobertISaar]

a SMALL amount of oil makes its way into the overflow resivoir on the MC. like, a drop or two every 1,000 miles. always has since ~35K miles when the water pump failed. apparently a lot more oil was making it in there than it does now. my father ran a bottle or block sealer in the cooling system and it is how it sits now. probably lost a headgasket back then(or maybe even warped the head?), but it has lasted to 204K without any real issues.

 

for oil to get into the cooling system, the oil would have to be at a higher pressure than the coolant for any transfer to take place. i don't think that would be possible if the LIM failed, since the lifter valley doesn't really have much pressure to it. i would think it would have to happen within the block or heads.

 

 

 

or, and this is my favorite answer, the previous owner wanted to lubricate the water pump.

[Crazy K]

very bizarre. oil would not leak into the coolant unless under pressure, which would show coolant in oil first if such a cross leak were to occur. I have experienced transmission fluid leaking into the radiator from a bad internal trans cooler, but it does show up as red.

 

ergo... clean it all up and watch it.

[Schurkey]

"Cleaning and watching" is not an option. This is a salvage vehicle with no title. Intention is to purchase vehicle, then transfer engine and transmission to a non-operating Cutlass Ciera. Finding oil in the coolant, and no obvious way for that to happen...I'm advising my friend to pass on this car.

 

Thanks, folks.