A dislodged gasket is also the first place I would look. Could there have been damage to the engine because of freezing, for example?
Is it water leaking, or coolant fluid?
1,000 hours is certainly not long for a diesel engine.
I would also check all hoses for cracks, and check connections are tight (and the hose clamps are the correct type, i.e. stainless steel).
Water leakage is immensely frustrating, as it often originates some distance away from where it is actually seen.
I am no expert in this area, but if you do not find something quickly, I wouldn't wait too long to call in an expert. Leaking outside the engine is fine, but if it starts leaking inside the damage can get expensive very quickly. I have learnt on my boat that that little problems like this emerge, and unless they are resolved, they generally turn into big problems quickly!
Good luck!!