I just picked up a 1999 CR125, but the coolant was mixing with the oil. What are all of the problems that could cause this? I am hoping it is just the impeller seal but need to know what other problems this could be. I already pressurized the cooling system and didn't notice anything leaking, but there was no air pressure behind the impeller seal so I couldn't tell if that was bad or not. Any help would be greatly appreciated. Thanks.