White milky goo on inside of filler cap

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My brother is looking at buying a pickup and I looked at for him. Everything looks good on it except when I looked under the filler cap it had the off-white colored goop on it.

I know condensation is a real possibility but there was a fair amount of it there and I am not sure if it would burn off with a long Interstate run. I saw it after a 10-15 minute test drive with a couple miles at 70 mph. Am I over reacting? My truck never has this, only a clean thin film of oily goodness under the cap.
 
Originally Posted By: dsmith41
My brother is looking at buying a pickup and I looked at for him. Everything looks good on it except when I looked under the filler cap it had the off-white colored goop on it.

I know condensation is a real possibility but there was a fair amount of it there and I am not sure if it would burn off with a long Interstate run. I saw it after a 10-15 minute test drive with a couple miles at 70 mph. Am I over reacting? My truck never has this, only a clean thin film of oily goodness under the cap.


"white milky goo" could be what mechanic types call "mayonnaise," and tht is sign #1 of a blown Head Gasket.

ive had cars w HG going out that hesitated, stumbled on acceleration.. this could be coolant fouling spark

white Plume of candy-smelling smoke, usually very big and doesnt go away in extreme cases = sign #3

pull radiator cap and check for "mustard" = sign #4

loss of coolant could be sign #5

lots and lots of pressure could be sign #6

milkshake looking oil could be sign # 7

how many of these does it have? Mayonnaise on a cap is usualyl never a good thing.
 
If there were a lot of that under the cap and down the oil dipstick tube and the oil looked even the slightest bit strange I wouldn't buy it.
 
This is quite common. My sons old Ford Ranger always had that and he just sold it with 354K on the engine. Often you see this with oil fill holes that are evelated well above the valve cover.
 
Goo could mean a blown head gasket, as you pointed out. On a lot of vehicles, though, the fill cap simply doesn't get hot enough, as tig1 had said. If it's farther away from the engine (farther away as in not right there), it can stay a little cooler and cause this condensation.

However, you said it's the same engine as your Ranger, and if in fact it is, and the fill cap is in the same place, then I don't know. I'd check the dipstick - it should give you a little better thought about what's going on, I think. Goo on the dipstick after the run = bad news.
 
Im gonna say its normal. I get that in the winter on my truck and wont "burn off" with less than a 40 minute drive.
 
Ford + winter = white goo undercap. (usually)

Like Tig said, the cap is raised from the valve cover.
 
I saw it on our Civic shortly after we got it. 50,000 miles later it never came back and we never had a problem. I'd be skeptical, but the vehicle may have sat for some time for some reason.
 
I once noticed yellow milky goo under the oil cap on my GF's VW Beetle. I panicked, thinking it was a blown head gasket. A quick google search showed that it is common on these cars and not a problem.

Like others have said, some cars just do this. But, find out if yours is one of the models where it is common.
 
Hi.

The white milky stuff is not due to an elevated oil cap or whatever. That's impossible. Ambient temperatures underneath the hood, combined with energy released from the combustion rxn, ensure that everything is hot enough that condensation will not form in large enough quantities to cause "goo."

Cars that have it, and the forums + owners say that "oh it's a common problem"...that's the manufacturer's engineering fault. Think about it. That stuff wrecks the engine. Would any manufacturer in its right mind want to design something like that? No. It's an engineering or assembly problem.

A blown head gasket is a more plausible problem. Because it contains water, and has a hydrophilic chemistry, it naturally has a lower boiling point and vaporization point. So, moisture builds up underneath during normal operation of the vehicle. That moisture collects at the top and combines with impurities to produce that "goo." Chances are, you will also find it on the top of the valve cover too.

The engine also could be operating in extreme conditions or in an area with high moisture content.
 
Originally Posted By: dtt004
Hi.

The white milky stuff is not due to an elevated oil cap or whatever. That's impossible. Ambient temperatures underneath the hood, combined with energy released from the combustion rxn, ensure that everything is hot enough that condensation will not form in large enough quantities to cause "goo."

Cars that have it, and the forums + owners say that "oh it's a common problem"...that's the manufacturer's engineering fault. Think about it. That stuff wrecks the engine. Would any manufacturer in its right mind want to design something like that? No. It's an engineering or assembly problem.

A blown head gasket is a more plausible problem. Because it contains water, and has a hydrophilic chemistry, it naturally has a lower boiling point and vaporization point. So, moisture builds up underneath during normal operation of the vehicle. That moisture collects at the top and combines with impurities to produce that "goo." Chances are, you will also find it on the top of the valve cover too.

The engine also could be operating in extreme conditions or in an area with high moisture content.


I'm sorry chief, but you are completely wrong. It IS caused by an elevated oil cap. I've seen it in several different Ford Modular v8s which I know for a FACT don't have blow headgaskets. Our own 4.6L for example has had it every winter for as long as I can remember. The underside of the filler cap is cool enough to cause condensation. When at speed, or idling, underhood temperatures in winter aren't reallly all that high.
 
Originally Posted By: dtt004
Hi.

The white milky stuff is not due to an elevated oil cap or whatever. That's impossible.


This information is incorrect. This does happen on some models of engine in the winter. My neighbor has a dodge Durango that has a plastic oil fill cap away from the rest of the engine. In the winter is gets this goo on it also, but only in the winter.
 
We have one car that has it, using M1 oil, because it is driven on very short trips almost all the time. Especially now in colder moist weather. It doesn't mean the head gasket has to be leaking.

I would go so far as to say every IC engine will develop this water oil mix goo under the right conditions, not some, all will, yours will. Maybe not seen under the only opening we see, the oil cap, but it will be in there. To me, that's why the one size fits all oil change interval, like Toyota's 10k for example, is faulty advice.
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I get this white [censored] on my Ford with a 460 motor too. I don't drive it in the winter much. Mostly just start it and put a stick on the gas petal at 1200 rpm every couple weeks but its in the cap too. heads are A-OK.
 
Some of us can tell dtt004 doesn't live in a terribly cold climate. Here's a question: It was -5 F on my way home tonight with a 15+mph headwind doing about 60 mph. Care to guess what the underhood temperatures were? While the coolant may be able to stay up around 195 ish due to the 195 degree T-stat, the outer surfaces of the engine and underhood temps are much, much, lower. Not even enough to melt the ice off the hood.

When the oil fill cap, like the one on my '99 F150 with the 4.6, extends well above the valve cover, you create a natural location that is much cooler and condensate will form, It has every year on that truck, and its over 192,000 now and runs like a top.

All that being said, I've got that SOHC motor in my '97 Explorer, and the oil fill cap is not on a long neck. I have never noticed the same "goo" on this cap as my F150. Something to consider. Perhaps the truck has been short tripped a lot in cold weather recently...
 
Originally Posted By: dtt004
The white milky stuff is not due to an elevated oil cap or whatever. That's impossible. Ambient temperatures underneath the hood, combined with energy released from the combustion rxn, ensure that everything is hot enough that condensation will not form in large enough quantities to cause "goo."


In California, fine. In a place with a real winter, nonsense. Just about every Ford I've had has had that problem, at least once in a while, even new vehicles, and engines with new gaskets and fresh oil and fresh PCV valves.

Some are more prone to it than others - notably, the ones with elevated oil caps or rather long oil fill necks. It was rare on my Town Car, but my LTD did it every winter, all winter, even after a rebuild, and it had almost exclusively highway miles. Overcoming -40 with a hugely overbuilt V-8 cooling system with a 2.3 L four cylinder under the hood is not a simple undertaking.
 
I had the white goo on a '78 Buick Skyhawk with the 231 V6 for about 6 years. Never did hurt the engine. As a matter of fact, it outlasted two clutches. I don't think its a problem.
 
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