This is how to clean an EGR cooler while it is still on the car. This car has 200,000km. 

The car is a 2001 BMW E46 M47 320D with a never before cleaned EGR cooler. Using a brush, oven cleaner, carburetor cleaner and fresh water I made it shine again. This way of cleaning should work for many cars that have easy access to the cooler. The cooler never has to be removed from the car saving time and hassle with the radiator fluid.