Low Coolant CEL light came on. Checked coolant reservoir - low. Added fluid drove one mile home. Noticed coolant brown and smelled like transmission fluid. Got to mechanic immediately. Transmission cooler inside the radiator had burst mixing coolant in transmission and transmission in coolant system. Had I driven it it would have trashed the transmission in a day or two. I knew exactly when it failed as I had checked the fluids literally the morning it failed so I knew it failed that night. Pretty big design flaw to have a radiator total your transmission.