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Red oily substance in expansion tank

(1999 BMW 323is)
in Longview, TX on February 16, 2011
What would cause a reddish oily looking substance in my expansion tank along with coolant level being extremely high?
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Popular Answer
on February 16, 2011
It sounds as if you have transmission fluid mixed in with your coolant. If the internal transmission cooler (usually built in with the radiator) has sprung a leak, its pumping transmission fluid into the radiator and mixing with the coolant.
on February 16, 2011
I'm sorry if you've gotten this more than once. My computer is acting up. Is it safe to drive my car with this leak and trans. fluid in my coolant? I have a 2.5 hour drive home.
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