Finally finished this one off on the weekend - had been waiting until I needed to dump the coolant anyway before removing the heat exchanger from the cooling system. 1. Remove one of the coolant lines from the heat exchanger and allow the coolant to drain (remove the bung from the radiator too if you are planning on a full coolant change) 2. Remove the second coolant line 3. Unbolt the heat exchanger from the side of the engine and throw it in the bin. 4. Remove the short hose that runs from the heat exchanger to the block. At the block end, there's a 90 degree plastic fitting with one of those connections where you push the hose further on, push the side tabs in, then pull back. It is a bit of a pain - you can unplug the smaller starter motor wire to get some more access for your fingers. 5. Once you have this length of hose removed, pry open the oetiker clamp holding the hose to the plastic fitting 6. Re-using a hose clamp, connect the other coolant line to the plastic fitting, and refit to the side of the block. So basically you have removed the heat exchanger and the short piece of hose. 7. Refill with coolant