Coolant leak

2005 GMC ENVOY
185 MILES • AWD • AUTOMATIC
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POPPI32CHULA
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Oil leaked into my coolant. I need to know what to do and what to do to fix the problem? Fridley, MN
Sep 1, 2017 at 3:06 AM
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STEVE W.
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Are you sure it is oil? If the coolant system has been exposed to air from a bad radiator cap or the coolant has never been serviced it can get a brown "goo" that looks like oil.

If however you are sure it is an oil, what color is it. If red in color it is a bad transmission cooler, located in the radiator. For that you will want to check the transmission fluid to see if it has coolant in it. If it does get a flush done and hope it was caught in time, coolant does bad things in a transmission.

Also you will need to change the radiator and flush the cooling system with a good detergent flush to remove the oil. Then re-fill with fresh dexcool.

If the oil is a dark color you should start with a pressure test on the cooling system. There are very limited ways that oil can get into the coolant. A bad head gasket is one. A pressure test would give you an idea of the issue.
Sep 2, 2017 at 12:34 AM
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POPPI32CHULA
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I think it is transmission fluid.
Sep 2, 2017 at 1:54 AM
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STEVE W.
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If so you will want to check the transmission fluid for contamination ASAP. Then do the flush and replacement of the radiator.
And as you will have it apart I would add in a second trans cooler, heat is a big enemy of transmissions. Extra cooling is easy and a lot cheaper than a burnt transmission.
Sep 2, 2017 at 2:02 AM