Sludge/Milky Coolant.

[Stayclassysam]

Hey Guys did an oil change a couple weeks back on my 6C GTI when I noticed my coolant level was sat below the “min” line, I topped it up with what I thought was the correct coolant, however, I just got back from a 4 hour round trip yesterday when I decided to check my oil and coolant level. My oil was perfectly fine, no milky residue on the dipstick not on the oil cap. The coolant reservoir however seems to have a brown milky layer sat on top of the pink coolant that I must say does smell like oil. The same residue and sludge is all covered on the side of the reservoir and is on the cap too. I’ve read things saying that it could be a head gasket issue but I have noticed 0 change to the vehicles performance and it was pulling brilliantly the whole time on the trip. Is there a reasoning behind this? I have purchased the correct coolant from VW and distilled water plus some radiator cleaner from liquimoly and was going to give it a full flush and refill tomorrow however if there is a leak is this not just going to happen again? Any help would be appreciated, I’ve just hit 40,000 miles and the car really is my pride and joy, having a head gasket failure really would be devastating.

Thanks guys!