the clutch fan works on a viscous, temperature sensitive clutch, when it is cool the clutch is disengaged, and spins the fan slower than the engine (not that you can tell by looking at it of course) and as it heats up the fluid expands engaging the clutch, when the engine is hot the fan should be engaged to the clutch and provide MORE resistance to turning than when it is cold.

however if you checked the fan after it had been sitting overnight, chances are that the clutch was locked up, since all the fluid would have settled to the bottom of the clutch causing it to lock up until it gets spinning and moves the fluid around.

 

So how hard is it to change out a water pump?

 

It should be farily straight forward. Pull the fan clutch off, anything that may be in the way of the pump, and pull the pump. I had a small hose that is a PITA to get to that goes from the water pump to intake manifold. If you have one on the 4.7 it's a good idea to replace it while you are there.

 

So I am going to have to take off the serpentine belt to get it out? Also have another question today been driving around the city of houston and it is a fairly cool day and the D did not overheat at all. What can this be a sign or symptom of? Is that still a problem with the water pump?

 

It sounds more like an electric fan issue if it doesn't overheat at all or a clutch fan issue. If the water pump is shot it's going to overheat regardless if it's cold or hot outside.

 

Yeah this is driving me crazy because I have replaced the fan clutch and the thermostat. I have not replaced the electric fan for the condenser which may be the problem. It does come on when I turn on the AC. It only overheats when I am driving on the highway and when it is hot outside. As I said when I was driving in Missouri in the cold last week the temp stayed at or below the 120 mark which is the mid point but when I crossed into to hot Texas it started getting really hot and over heating. I don't really know if I want to spend the money to change out the water pump and that not be it. ANY other suggestions you may have? Could the electric small fan be going out ?

 

Yes!

Check that electric fan!

 

What is the best way to check the fan? It does come on when I turn the air on.

 

It is supposed to come on with the a/c and when the truck gets to I believe 210 or 215. The thing is that after you get to 35 mph and above you have enough airflow over the radiator that the fans aren't really going to make a difference. How did the old coolant look when you drained it and did you have a 50/50 mixture of coolant going back into the D when you replaced the t-stat? I know these questions may sound dumb but I have to ask. Did you check for cold spots on the radiator yet? How did it look?

 

+1 on checking the radiator for cold spots. If you have a plugged up radiator it would cause this hands down seeing that you already replaced the T-stat and clutch fan.

Did you burp the system when you did the T-stat and where did you get the T-stat you replaced?