# What is yellow foam residue inside oil cap (this doesn't look good)



## milanski (Mar 11, 2008)

Hi all,
A picture is worth a thousand, and I figured someone must have seen this before.
It's a 1999.5 (IV) Jetta, 2.0L, manual, about 125k, recent oil change, brake fluid, and coolant changes. I got a CEL, and when I took off the oil cap (it has a steady leak from the crankshaft seal, so I figured the CEL was due to low oil), I saw this.
What have I got here? And what do I need to do to fix it? Thanks!










_Modified by milanski at 12:52 PM 1-9-2010_


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## tdogg74 (Mar 1, 2002)

*FV-QR*

its where peanut butter is born.


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## Jay-Bee (Sep 22, 2007)

*FV-QR*


_Quote, originally posted by *tdogg74* »_its where peanut butter is born.


Haha,
CEL for low oil? Unless you drop so low there is none on the dipstick that ain't gonna happen.
I've seen this before... in the DIY/FAQ thread!
I don't seem to be getting much "goo" this winter, but when I check my oil and open the cap I have a lot of condensation/water that I wipe off.
You can replace the 2 seals on the breather and oil cap... seems to help some people, it's the way our open PCV system is setup, it's gonna happen no matter what.


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## jetta09black (Mar 12, 2009)

*Re: What is yellow foam residue inside oil cap (milanski)*

It is a by product of the petroleum based oil (mainly sulphur) ... usually only happens in the cold weather...


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## Cee-dub (Feb 20, 2007)

*Re: FV-QR (Jay-Bee)*


_Quote, originally posted by *Jay-Bee* »_I've seen this before... in the DIY/FAQ thread!

Yup... http://forums.vwvortex.com/zerothread?&id=2526976


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## milanski (Mar 11, 2008)

Thanks for the responses (even though it was a noob question).
BTW, I pulled the code for my CEL. Turned out to be 16824 (P0440 (evap control problem). It was a qt low on oil, but any idea what might cause this code?


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## makman (May 15, 2014)

This may happen if your oil cap is not good. Or you dont heat the car enough. Short frequent rides in cold weather may cause this goo


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## ps2375 (Aug 13, 2003)

You realize this thread was *4 years old*...


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