Oil coolers usually fail because the threads get damaged and they are no longer usuable. This usually happens when you go to replace the oil cooler hoses or remove the oil cooler for some reason. Those aluminum threads on the cooler seize to the steel nut on the hose and when you go to remove the nut - it is all over for the cooler.
Problem & Solution
Common among these chassis:
In this free video Kent will explain the problem and explain what we are doing here at Mercedessource to provide you turbo diesel owners with resources to keep your old Benz running.