My 2001 Forester recently overheated and had to be towed home. I'm no mechanic but I may attempt to replace the radiator which is leaking badly. My only question has to do with a thick mud-like sludge that blew presumably from the radiator all over the engine when it overheated (see pictures). What is that? Is oil mixed with coolant, indicating a head gasket failure? I removed the bottom hose and the coolant that came out of the block is a dark green and doesn't appear to have oil in it. Also, no white smoke from the tailpipe. I bought the car from a friend who had the head gasket repair done about 5 years ago at a local dealership so I'm hoping it's still good.