Originally Posted by
harbor
Maybe it's residue from the prior owner's car?
If coolant level is steady, catch can is correctly installed and the hoses and passages are clear, I'd let it go for another year and see what it looks like then.
The previous owner said he emptied it before sending. I sent him a PM asking about it. I didn't clean it out or check the hoses before install. I'll take it apart tonight and see if the hoses or anything is clogged.