CLEANING OIL COOLER

One of my portable air compressors, an Atlas Copco XA125Dd, has been running at higher than normal temperatures (air end) with the result that the oil started to 'break-up' and become lumpy. The air separator element became drenched in oil and was partly 'crushed' (see attachment). I am servicing the entire system now but and faced with quite a task when it comes to cleaning the 'sealed' oil cooler. I would like to get some advice on what I can use/do to clean all the cores so that this cooler functions normally. I thought of using a solution of caustic soda but since the cooler is made from a alloy rich in aluminium, I am afraid the soda will damage the cooler. Your advice PLEASE!! Kind regards Faisal MALAWI, Africa