ok, the 5.9 is pretty simple, cooling wise. from what im hearing here it sounds like you have a faulty thermostat. it could be possible you put the thermostat in the wrong way.... if your fan clutch was bad, the fan would be engaged all the time constantly pulling air. you may also want to check the waterpump pully for play as they tend to not last very long , especially if you got a cheapy valuecraft unit. a bad fan clutch can cause a waterpump to go south quickly
when you flushed the coolant, did you flush the heater core? could be some gunk in there causing problems, not common but ive seen it happen.
to check the fan clutch let the motor cool to ambiant temp. and see if you can spin the fan blade, if not your clutch is siezed.
a popular mod for alot of people on here is to switch out the clutch fan for an e-fan. fyi.
havnt heard any sludge issues with the 5.9, though the biggest problem with this motor is the plenum gasket. search the 2nd gen ram forum for that and a plethora of info can be found on that problem.
also, welcome to DF!
Last edited by nim81; 06-08-2010 at 05:12 PM.