There is oil in the coolant.
First, you have to determine if it is engine oil or transmission fluid. If you have an automatic transmission, then there is a heat exchanger in your radiator. Transmission fluid runs there in two hoses. If it cracks, you will get transmission fluid in the coolant, and coolant in the transmission. If it is engine oil, check the dipstick and see if there is coolant in the oil. It will look like brown foam. This is most likely a cracked head or bad head gasket. A qualified mechanic from YourMechanic can come out and diagnose your issue, locate any leaks, and make any necessary repairs.
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