Name this crud. Should I be concerned?

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Laminar Lou

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This is the oil cap of a 2002 Toyota Tundra. I have Amsoil 0W30 in it and I use LC20 as well. It's soft and easy to clean. I cleaned the oil cap 700 miles ago so this is the accumulation in 700 miles. What is it and should I worry. What is strange to me is that the oil fill neck has got to be 9-12 inches off the motor so my guess is this is material that has condensed and not splashing on the cap. I live in Southern California so the climate is not extreme. Just in case it isn't obvious, the junk to the right is a swipe from the cap. The cap was originally covered. Here is the oil filler neck (but it looks normal to me)
 
That is a mixture of water and oil. It's on the plastic and not the metal neck because the plastic doesn't get as hot as the metal, so water condenses on the plastic. If you never whipe it off, it will harden over time and can turn into a more malignant sludge but at least it's only on the fill cap (apparently). Don't blame the oil or LC. This can happen to any oil.
 
Seems like a lot to me, and here's why.... I had a leaking valve cover gasket on my 2.5 iron duke engine years ago, so I removed it and thoroughly cleaned and degreased the inside of the valve cover while it was off....to the point it had NO residue of any kind on the inside. Re-installed, drove around a while, checked for leaks and parked it for the night. The outside temp was around 40 degrees over night. The next morning, I had the same #@$%! under the oil cap, but not as much as you're seeing. It freaked me enough to do an oil change, where I found a pan full of normal looking oil...no 'cream'. So, I filled it back up with new oil and just ignored it for a couple of weeks, and the cream never re-appeared. The only thing I could attribute it to was condensation forming on the inside of the valve cover due to a completely clean surface, and then oil mixing with it. There was no other explanation since it went away as suddenly as it appeared, and there were no other signs of a coolant intrusion. Just clean your cap and keep an eye on the oil in the pan....it's more important than the stuff on your cap. If it persists or worsens, it will eventually have to affect the oil supply and at that time you can determine that you have a coolant intrusion.
 
Thanks for the replies. I will keep my eye on it, but it seemed like it was a lot to me as well for only 700 miles. The truck only sees about 5 miles a trip, 4 times per day. I have had UOAs on this truck recently (back in September 06 or 2300 miles ago) and there were no signs of coolant leak (and the report was very clean). I was thinking of doing a UOA in march (the 6 month point) , now I know I will do one. My intent is to take this oil to 1 year but maybe the UOA will change my mind.
 
You may have a leaking gasket..BUT before you freak out (that's what I do when I have a leaking anything)try a few things first. Check coolant level, top off, mark the level and monitor it. Same with oil level. Clean your entire PCV system. I would even replace the valve. Take the vehicle for a 50-100 mile freeway trip after cleaning off the cap again. Run it another 500-1000 miles with no add in coolant or oil and re-check. If you are still getting foam...then it's UOA time to see what's making it's way in there.
 
I concur. It looks like it's only condensation goo. It's an emulsion of oil & water. Comes from the condensation on the oil cap mixing with oil splash. Short trips in cold weather that don't allow your engine to warm up and drive away the moisture are your cause. I take my vehicles the long way around to get to work to keep this icky stuff away. I also take a long drive on a weekend morning every now and then to assist...about a good cigar's worth of drive.
 
My mother's BMW does this like crazy. I whiped it off one morning, drove it some that day, and checked it again and found more of that crud. It can sprout up in very little miles/time!
 
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You may have a leaking gasket..BUT before you freak out (that's what I do when I have a leaking anything)try a few things first. Check coolant level, top off, mark the level and monitor it. Same with oil level. Clean your entire PCV system. I would even replace the valve. Take the vehicle for a 50-100 mile freeway trip after cleaning off the cap again. Run it another 500-1000 miles with no add in coolant or oil and re-check. If you are still getting foam...then it's UOA time to see what's making it's way in there.
I changed the PCV valve about 2000 miles ago(just as preventive maintenance at 5 years old). It doesn't appear to be digesting coolant, but I'll mark the level just for fun and watch it. Would a leaking PCV system cause this as well? Maybe I didn't get everything locked down correctly when I replaced the valve.
 
I have a ford 300 I6 with a raised filler cap on the valve cover [to prevent people from cutting their fingers off on the rocker arms if the engine is running] It is raised perhaps 2"; I get a FROZEN version of what you have in the winter; even when the engine is @ full temp. A "for sure" coolant leak is a bit alarmist.
 
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Seen similar crud with a couple of cars that only ran around town; rarely, if ever, out on the hyway. Engine never got hot enough for long enough to evaporate the condensation inside the engine. An Italian tune-up might clear it up for a while. My 2¢
 
That crud is likely there due to the high number of short trips. I see a number of posters suggested that it might be a head gasket or coolant leak. While a coolant leak is certainly a possible cause, I'd be fairly certain it's just condensate from the short trips. Why: 1) short trips 2) UOA came back negative for coolant and 3) it's not "digesting coolant" If it were my car, I'd just drive it on a decent length trip on a periodic basis, like once a week or so.
 
Do not worry about this it is not a coolant leak at all. Not only does your UOA show this but the rest of your oil did too when it was drained. Condensation will try to form on the highest point if it can. When You add an oil fill neck that is 6 inchs' long and has a composite/plastic cap you also get fast cooling rates. The more around time driveing you do and the cooler the ambient temp. the more of this you will see. It also is common on Dodge 4.7 liter V8 and most BMW and Mercedes V engines as well. It is a non issue! Nothing needs to be done and no worry is needed!
 
Coolant leak can occur for any other reason 1. A hole in radiator from rock chips 2. Heater core 3. Oil cooler seal Idiot light should come on if it goes below the sensor.
 
I think more of the concern lies in the 5 miles/4 times a day; that truck needs DROVE! Take that baby on the highway at least twice a month for nothing less then 30-50 miles; in my honest opinion, no oil is gonna keep the cobwebs out of that engine - she's not getting hot enough.
 
Lou, you've got to give that V8 some work to do, get the temp up, and wipe that crud out with a rag. Take it for a long run and go up some steep hills. That big engine does not have much to do putting around on short trips.
 
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Lou, you've got to give that V8 some work to do, get the temp up, and wipe that crud out with a rag. Take it for a long run and go up some steep hills. That big engine does not have much to do putting around on short trips.
Yeah but working that big V8 costs a lot of money! Especially at $3.09 for regular (that was yesterday's price). I didn't buy the truck as a commuter car, but it turned out that way. It was great for hauling motorcycles, but now all we haul is a baby and the minivan does a better job then the Tundra. Funny how life changes but I digress... The Tundra does have an oil cooler that runs through the radiator. In my case it acts more like an oil "warmer" using the radiator temp to get it in range faster. However, I still don't think that oil ever gets up to temp with a 6qt capacity. But with the UOA showing <.1% water I think the "cap goo" is just isolated to the cap. I will continue checking in warmer weather - it is supposed to be in the 80F-90F this weekend!
 
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