Condensation on My Oil Filler Cap? (Inner side of cap.)

2001 Dodge Dakota Quad Cab - 235 HP, V8,4.7 litre Fuel Injected, overhead cam engine. Regular Maintenance followed, 30,000 miles (about 13.5k per year avg) Auto trans, no towing, modest hauling in bed. Warranty good til 36k.

Yep - unscrew oil filler cap, go to add new oil and there appears to be clear droplets on filler cap. Looks like heavy condensation, for lack of a better description.

Engine runs well, did notice valve chatter above 3500 rpms or under heavy load. (Load = load of acceleration on engine, demanding low end torque and/or high rpm for you non-gear heads).

Gear heads? :confused: I have no reason to believe there has been any breack of cooling fluids into engine, because I’ve experienced that in some other vehicles, and it results in fouled plugs, poor cooling, and poor drivability.

This will be brought to the dealer for warranty work, but I know there is sufficient gearhead knowledge here to help me know the straightdope on oil.

I’m pretty car savy, but can’t see this objectively because it’s my truck. Kind of like a doctor who can’t be his own patient.

(hey, on a side/curious note: this engine has a plastic intake manifold. Yes, the actual manifold is indeed plastic)

A follow up question relating to your question: Do you live in a very humid environment?

Scenario: Air trapped in your crankcase with higher than normal humidity, with a little pressurization and depressurization could cause temperature to dip below the dewpoint. Water then condenses out of the air in your crankcase?

Just a theory. I have never experienced this, but I live in the Southwest…hence the theory.

Humidity: North East United States. Philadelphia area. Not humid this time of year. Cold and dry mostly, with occassional snow fall.

Couple of things here.
All internal combustion engines have blow-by. (escape of combustion gasses past the rings into the crankcase)
The burning of gas creates water, the cleaner the engine the more water created. Some of this water goes into the crankcase with the blow-by.
When the engine is at normal operating temp the water boils off (Oil temp runs upto 250F)
However if the weather is cold, or many short trips are driven the oil does not get hot enough long enough to boil off the water. This results in condensation inside the cooler parts of the engine (oil cap)
We often see this on cars that are delivered fresh off the boat from Europe as they have been started countless times without ever being warmed up.
We leave the engine running during the new car prep process and that generates enough heat to boil off the water.
Sometimes the condensation can appear milky in color. This to is normal.o

Rick is correct.

The clear droplets you mentioned indicate water, not engine coolant (which is 50% antifreeze). If you were getting coolant in the oil, you’d have to be losing coolant from the cooling system–if it’s staying full, it’s not leaking. Also, coolant in the oil is usually detectable on the dipstick and/or when the oil is changed. If the only thing being observed is moisture on the filler cap (and perhaps on the inside of the valve cover), condensation is the plausible explanation.

Well, I feel better. Only slightly concerned because 95% of my driving is long trips (30 miles). But, the oil was at the end of it’s life (5k) and the engine wasn’t very hot because the oil was being changed.


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