I have been using my 2004 ford escape 4x4 v6 for nearly 7 years now since my dad gave it to me. I am not a very technical guy when it comes to car maintenance but I see to it that it is always tuned-up and changed oil every 5000km or so. But this past week I noticed on my garage floor that there is a puddle of brown gooey liquid accumulating so I decided to check my engine. Low and behold I found out that my coolant on my reserve tank has turned brown and very gooey like it was mixed with oil and now everytime I turn off my engine it would overflow through the overflow pipe at the top of the coolant container. Can anybody guess what type of problem my car has before I go to my repair guy so I would not get ripped off. A friend suggested that I might have a leak in my radiator that is why oil is mixing with my coolant. Btw I am not experiencing any overheating. Any help or comment would be much appreciated.
Oil in the coolant or vice versa is usually a sign of a failed head gasket and/or a cracked/warped head. Other symptoms include white exhaust (when not caused by low temperatures, obviously), exhaust gas in the coolant (causing bubbling in the coolant or "burping" of coolant into the expansion tank), and a high/fluctuating temperature gauge.
The usual means of testing is to take a combustion leak detector (like this one) to the radiator. You take the radiator cap off, put the tester there, and suck in some of the air there. If the fluid changes colour, there's combustion gas in the coolant.
As Gabriel Mongeon suggests, a transmission cooler leak is another possibility. If this vehicle has an automatic transmission, it would have a transmission cooler, which could be another source of the contamination.