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QI would like to change the coolant in my Isuzu 4.2 engine. Where can I find the plug or tap to drain the water? DES DOUGHERTY, via email
AI don’t know if that particular engine has one, but they usually do, though. Imagine looking at the front or rear of the bare engine, then working up from the sump there will be a short vertical section of the block that then turns inwards at both sides before returning to the vertical right up to the cylinder head. The lowest point in the water jacket is just above the parts that swing inward and on the upper vertical section. Look along both sides of the engine at that height for a brass plug or a tap, sometimes on the end of an elbow extension. Even if you cannot find a plug, removing the lower main cooling hose connection on the engine water pump will allow most of the coolant in the engine to drain.
If this is a skin tank-cooled narrowboat it is probably easiest to drain the whole system from the lower hose on the skin tank. If you cannot easily get to the lower hose connection, free a joint on that hose where you can and hold the hose in the bottom of the boat so that it drains.