I was noticing a fast ticking sound when accelerating, on my 2001 HSE 4.6, for the life of me I could not work out what it was. Everything looked good under the hood, then it dawned on me to check the water pump. I could move the fan quite a bit, which allowed the fan to move out of position and just touch the top hose clamp, causing the ticking sound.
Even though the water pump bearing was obviously shot, the pump made no unusual sounds, and the temperature gauge was normal, no signs at all, which is a bit scary. I have read other P38 owners experiences with water pumps just letting go all of a sudden.
So with a new water pump in, all is good once again, but I would suggest a check of the fan movement next time you are under the hood, might save you a breakdown sometime.
Hope that helps someone!
Cheers, Pete.