I have a 2000 P71. Ever since i got it two years ago, the antifreeze has been brown. I finally did a flush and fill two months ago, and it it brown again. I figured the brown was due to mixing yellow and orange, but now i know that there is something up, as i did a thorough flush and filled up with a 50/50 yellow antifreeze and water. I know a blown head gasket will mix the coolant with the oil and oil with the coolant, but this doesn't look like the oil floating on the surface of the coolant as ive seen before. Any ideas?