Black95MustangGT

Today i opened my radiator cap and the fluid was solid looking, like it froze. And then i had to go to work but my step dad worked on it and he said the fluid was really really really cloudy, but they checked my oil and i didnt have a drop of it in my car. Thank god i didnt drive it any more, but yeah. We put stop leak in my radiator since it was leaking and it did stop leaking but then it started to this morning. Could that be because of my oil? or what? its really confusing and we are all confused about what it could be. Why would where the antifreeze goes freeze?