Have youever experienced a milkshake coolant in your radiator. Never think its a modern coolant, your oil cooler is just bad and needs to be replaced.

I just finished working on a 2011 Mercedes Benz C300, which had this problem.
Steps to fixing the problem on a C300
1. Observe where the milkshake colour is. If its in the sump, its probably a blown gasket but if you see it only in the water reservoir then the oil cooler is bad.
2. Remove the radiator hose and allow the coolant to flow out.
3. Loose the power steering reservoir so as to get access to the fasteners on the oil cooler.
4. Loose the fasteners on the cooler and bring it out.
5. Replace the old damaged oil cooler with the new one. Make sure you change the seal between the oil filter cup and the oil cooler and also use a good sealant gum on the seal between the cooler and the oil filter cup.
The oil cooler spoils when the seals inside it gets bad.
6. Fasten the power steering reservoir back.
7. Flush the entire engine/radiator water way. This can be done by pouring water into the reservoir with the hose sending water out of the radiator not fixed in its position. You can also add detergent ( this is the local way) as an emulsifier.

8. Wash the water reservoir.
9. With the accurate measurement add coolant to the vehicle.
Visit www.mekkanics..com for more car gist