Gunk on my oil cap

I was checking my oil the other day and when I removed the cap there was this whitish film stuff and gunk on it. This is the first time I have noticed this and was wondering what is it, what causes it and should I be concerned? My car is a 2002 Kia Sedona Mini van 6 cylinder with about 147,000 miles on it and it has had regular oil changes for the past year plus that I have owned it.

Check you level of coolant, and look at the oil on the dipstick. If the oil is kind of 'milky" looking there could be coolant getting into the oil. This occurs when a head gasket or the head itself goes bad. Any overheating events recently? This is not a good sign and something you indeed should investigate.

The description sounds a lot like what you get from having coolant mix with the oil. What does the oil on your dipstick look like? If it is coolant in the oil this is very bad and will kill your engine pretty quickly so if you start that engine again I’d make it for a really short drive directly to a good mechanic for evaluation.

The most likely causes for coolant mixing with oil are breached head gaskets or intake manifold gaskets.

The white film under the oil cap is usually caused from driving the vehicle on short trips without allowing the engine to come up to full operating temperature to drive moisture out of the crankcase.

Another cause can be coolant leaking into the crankcase. But if the coolant level never drops in the vehicle, then the most likely cause is short trip driving.


Coolant levels have not changed since I have had van, not overheating issue as I monitor it closley given age, and not one bit of “gunk” on dip stick at all, stick clean. Oil when changed out has been gunk free. I do alot of short drives, basically back and forth to work is all I do which is about 28 miles a day, 14 each way. Do some minor driving on teh weekends, on average do about 150 miles of driving a week, all in city stop and go driving for the most part.

Is your minivan warming up as it should? A thermostat that is stuck open will not let the engine warm up and this can cause the gunk you are seeing under the oil cap. If the temperature is coming up as it should, then short trip driving may be the cause. It used to be that some brands of motor oil seem worse about having this gunk build up than other brands, but I don’t know if that is true today. If you changed brands of oil, that may be a possibility.

I had the same problem with a 98 Ford Windstar and a 95 Dodge Dakota from short trips. Although a 14m drive should be enough to burn off the moisture. I replaced the PCV valves on both vehicles and that seemed to help.

I would keep an eye on the coolant level, loss of coolant could indicate a intake manifold gasket leak.

Any combination of short trips, an open thermostat and high humidity can cause the sludge to accumulate. If the oil remains bright it is unlikely to be a serious engine problem.

Van warms up the same way it always has, no problems there. Engine is running great given it’s age and milage. Engine starts right up and runs smooth. Over the 12,000+ miles and year and a half I have owned it I have had to add antifreeze once and it was like maybe a cup or to and that was back in early 2011, since then the level has not changed one bit. The dip stick has not shown any gunk at all at either the tip or at the top which I have had happen on other cars I have own. I cleaned the cap and will monitor it.

Usually V type engines have the PCV valve in one valve cover and an open vent to the air filter housing on the other, Which vent is on the cover with the filler cap? Any accumulated moisture will evaporate when hot and rise, It will re-accumulate and condense at the highest point when it cools if there is no venting.

I do apologize Rod, I kinda don’t understand your question and I am sorry. the oil cap is at the front of the engine and my air filter housing is just to it’s right if that helps.

I’ve noticed this problem with cars I have owned in the past. I had a 2 mile drive to work which really didn’t let the car warm up. I would have walked, but there are no sidewalks. I just changed the oil at the severe service interval. I didn’t think anything was wrong since the coolant level didn’t go down, there was no gunk on the dipstick, and the oil didn’t contain any gunk when I did an oil change.