I'd think maybe thermostat is not opening right. It has to allow water to flow through the system to get hot water into the radiator, don't recall if you changed stat, if you did not use OEM that may be a problem, there have been reports of aftermarket not opening soon enough. Belt route proper on water pump?

 

Hey Buzz.. whats the proper belt route on the water pump?? im 99% sure mine is correct but.. what the heck

 

see attached from RAVE.

 

Just a note I learned way back when.. when putting on new belt on discovery 03 when I didnt have a diagram... I looked at pulleys... if they had teeth, then teeth side on belt faces toothed pulleys thus smooth on smooth... was pretty self explanatory at that point... I ended with the pulley to left ( Alternator ) of A/C pulley while holding belt tensioner loose .... in my experience was pretty easy ... might need cheater bar on wrench if upper arm strength is at a minimum.... Im 5'8" and 220lbs of mean Texas now Floridian ( dont tell my fellow Texans! lol ) so I didnt need the cheater bar... lol