noise @ idle any ideas?

[Kaka-x]

hope am in the right place for this.
I have a 98 explorer sport 4.0 v6 vin x so i take it that its the OHV not the SOHC engine.
well i have been hearing this rattling noise @ idle speed. it sounds like a diesel engine and is starting to get more prominent.
At first it would be there sometime and sounded like marbles going down a metal drain pipe, then it stopped and at last oil change (motorcraft synthetic blend with fords filter) it came on right after the oil change and has never gone away, i have changed to conventional castrol oil but still the noise is there.

Can anyone confirm that its the timing chain tensioner thats going bad and how hard/ easy fix is it.
I have read that this problem is common in the sohc model so am kinda confused
SUGGESTIONS WELCOME and thanks for your time

 

[Kaka-x]

i decided to take out the serpentine belt and listen for sounds.i have called the dealer any the guy says that the timing chains problems are more in sohc engines.
it might be the valve train even though its more prominent around the bottom half of the engine. i will try some seafoam thru the booster vacum hose and see if it helps.
i just hope its not engine problems