Yellow gunk in oil cap..
 

Ive had yellow gunk in my oil cap for about 8,000/km everyone says its short driving, but Ive done nothing but hauling for an hour each way for a week straight, other suggest its blow buy? never herd this term.... don't think its radiator coolant cause the yellow gunk is usually frozen in my oil cap, how would i tell if its radiator coolant thanks

Start by checking the dipstick after it has sat for a while. Is there a murky color to the fluid on the dipstick? Does it look like layers as in the oil is above another line of a different fluid? Does it look like pure oil or like chocolate milk? The odor may help a little also as the smell of antifreeze is pretty pronounced and the smell of used motor oil is also pronounced. I understand what you are saying about taking only longer trips but the engine design can still trap some condensation that collects in the valve covers and oil fill cap. I get the same milky goo under the cap but don't give it any thought except to wipe it off when I change the oil. The antifreeze level is consistent and the dipstick shows only oil. A gasket letting antifreeze into the crankcase would result in a loss of antifreeze and a murky fluid on the dipstick.

Edit: Finally, if you change the oil yourself, drain it into a translucent container and look at the contents for the same layer effect where the oil would be above the antifreeze. Observing the drained oil will also give you a clearer look as to whether it is just dirty oil or something else...

Its normal they all do it its condensation in the winter only summer it stays clean
mine does it every winter and I have no leeks from anywhere including anti freeze

Ditto: My thought is also condensation: especially in colder weather. x(

+2. I have been driving F150 for 13 years and always have this problem in the winter. So far I have no leaks of oil and antifreeze. I was told that it is due to condenstion. I just wipe it off at oil change. Hope this make you feel better.

I've had this problem on every vehicle I've had for 35 years that fill the crankcase through the valve cover. The valve covers tend to stay cooler and cool faster than the rest of the engine when you shut it down and when they go through the dew point they pick up a little water on them. I'm guessing that the inside of the valve covers pick up this water too, but the valve oiling spray washes it off and "burns" it off in the hot oil. The oil cap is usually positioned where there is no oil spray so it doesn't get washed off. Probably why they used to recommend more frequent oil changes in cold weather. Since it's freezing, it not antifreeze. Like others have said, just watch the oil on your dipstick. If you have any reason to suspect anything major, get an oil analysis done to put your mind at ease.

Same thing, condensation in winter. Wipe it off and keep driving.

I have the same issue. BUT, I am don't know if I have a greater amount that everyone else. I cleaned out my filler cap on 1/22/10 and it is almost full of this yellow gunk. Are all of you getting this much? I have also been keeping an eye on my coolant level and there is not a noticeable difference.

I would think that a lot depends on your driving habits, your local climate (such as temperatures if parked inside a garage, weather it is insulated or not; temperatures outside and how often the truck goes from one extream to the other) and the humidity.
My garage is insulated and never gets below freezing unless I leave the door open. So my truck sits inside at say 40 degrees and goes outside where it is 10 degrees, engine warms and sits and gets cold. Then when I return it goes from warm to cold in a temperture above freezing, leaving a puddel of melted snow on the floor, which created a lot of humidity (see where I am going)?
I would defiantly keep an eye on coolant levels, and consider how long its been since you changed your oil.

Short driving cycles allow moisture to accumulate and never be boiled off. Also, I'm not sure how the crankcase ventilation system works on the 5.4 3v, but I would check to make sure your PCV system is working correctly. If your truck has a PCV valve I would replace it.

Ok, to answer a few questions:
1. I live in NW Ohio weather is 10-35 degrees(F) outside with off and on rain/snow. My truck then sits in a heated garage @ 50 degrees(F). My primary drive is to and from work 10 miles/15-2o minutes and to pick up daughter which is approximately the same.
2. I replaced the PCV valve approximately a month ago with no change.

Would you guys be worried after knowing that?

Sorry to take over your post Birdman.

Buck-

No, knowing all that would not concern me any more about the stuff under the oil fill cap. As others have said, the water vapor condenses repeatedly under the cap and, in this weather, does not get warm enough to completely evaporate. The warm, damp garage probably only adds to it so I wouldn't give it any more thought.

yeah buck what do you drive, is it 04 and up 5.4 cause they are suppose to have a maintenance free PCV valve as Ive done a lot of research on that lemme know thanks everyone

Yes it is a 2004 5.4L.

Yeah, I had read that it was maintenance free, too. I do know they replaced it, because I asked for the old part. But, what does maintenance free mean? Is it never going to fail? I doubt that. They had just checked into a few different things and one of them was that there was quite a bit of resistance through the PCV. I don't know what ohms it was reading and I am not electrically minded.

I am still worried about the amount of the foam I am getting. It is not just a coating, in 2 weeks (500 miles) it will fill the bottom of my filler cap. If everyone else gets that much then I will feel better and let the issue die.

That is quite a bit more than I get.