1. Make sure you have a set of replacement gaskets on hand. They will need to be replaced when finished.

2. Punch mark the position of each bonnet prior to removing them. This will help with lining them up correctly when put back on. Remove both oil cooler bonnets and visually inspect the tubes and the bonnets. Inspect the dividing ribs on the bonnets for erosion as bypass of water that past these ribs can limit cooling.  If needed, replace the  bonnets with new.

3. Determine the tube size of your particular oil cooler.  Using a cleaning rod, remove buildup from inside the tubes.  If the tubes are plugged and cannot be cleared of buildup, your cooler will need to be replaced.

4. Once the tubes are free of debris and buildup and the bonnets have been inspected, replace the bonnet gaskets and install the bonnets.

5. If you suspect an oil cooler leak, you can block off the bonnet connections and pressurize the cooler on the water side.   Pressurize with a   minimal 30-45 pounds of air for 30 minutes.

If the cooler maintains PSI, it is good.