This may have been brought up before but after a quick search I couldn't find anything. I recently heard about these bags which are located inside the MQB engines (may be others) within the coolant tanks. They are small bags of silica which are designed to preserve the life of coolant but over time it has been known for these to burst and cause mega problems within the coolant system. Not a good thing for cars out side of warranty! Anyway, here is a short video (not me) of how to remove it, I will be doing this today hopefully if the weather isn't too bad!