corsa c water bottle?

hi again my corsa c replaced head gasket bolts etc its been 250 miles since why am i seeing bits of mayo like items floating in my water bottle also greece in bottle iput finger in bottle and scrape bits of black oliy stuff its not alot only a bit i took bottle of last week cleaned it all out now its back could it be old crap oil cap is ok dip stick is ok thanks

s
March 2011