It was pretty strange what came out. It wasn't mucky coolant or large chunks of debris, rather it was a lot of tiny pieces of what I would call dried up coolant. There was probably just enough of them to fill a milk cap with. That's all it took to get the heat nice and hot again. I will be keeping an eye out for it though. I do understand that at 200K miles, the heater core is a candidate for being shot. For now, I'm one happy guy.