Never just rains, but I caught this one before it started pouring! Almost literally too... Got home from tonights Zed Shed session and was just about to turn the engine off, but heard a faint knocking noise. Figured it was coming from the engine bay, so popped the bonnet - noticed that the fan blade was spinning off center and clipping part of the front of the engine - hence the knock Having stopped the engine I could just make out that the fan blade is separating from the viscous coupling. So much so that I can move it by hand and it's almost due to come off completely. That most likely would have been the end of the radiator. Will have a better look in daylight and see if it's just the bolts coming loose, or if something has physically failed. I'll pop some pictures and a video up too once I've done so.