Okay well I am helping my sister with her 1998 Ford Mustang. She seemed to notice her car running hot at idle. I told her to check the anitfreeze(which means for me to check it) I did and she was low. Like I couldn't put my finger down the radiator and touch the antifreeze low. Well I decided to look in there with a flash light and noticed a brown color floating atop of the antifreeze, my guess is either oil or rust. I took a long screw driver and just retrieved some of the liquid on to the screw driver and saw this:
The red boxes are the concerning part. I checked her oil and her filler cap and there are no signs of coolant or water in the oil. So this is what is puzzling. So I filled up the radiator. I poured in a lot, and it just kept burping it down. Until finally, after more than 3/4 a bottle of anti freeze it stopped(including filling the reservoir).
If it is oil then my guess is a cracked head gasket or a cracked head. She freaked when I told her this.
Just note that the antifreeze didn't have an 'oil' smell to it.