300tdi idle problems i think ????

hi just wondering if anyone has had same problem or knows a cure my 300tdi has always run faultlessly but today seems to be idling a tad higher than normal im sure it sits a little bit under 1000rpm normally now its sitting dead on 1000rpm idle it sounds to me like the engine note on idle has changed hence noticing the idle rpm i did over heat it the otherday trying to get out a muddy puddle boiled the coolant but it hasnt overheated since and no i got out on my own honest a freelander did not pull me out he was just watchng from the rear view mirror but any help would be great

just been out and adjusted the idel speed now the truck seems to be lagging hunting with the fans or lights at about 750rpm but as soon as you turn them off it goes back to 1000rpm if you move steering it dips to about 750rpm and stays there untill you blip the throttle and then it sits at 1000rpm again

With it slightly idling high and you overheating I'd of thought (but only my opinion) that there was air getting in somewhere
but now you have adjusted idle and it's dying with light and fan on could be alernator trouble I'd of thought but could be completely wrong

thanks for the reply mate maybe ill check it out