Yep, the Astro's got a pretty big fan under there. You will always here a little bit of a roar when the van is sitting still, because the fan never really completely stops, especially on a cold morning when the fluid in the fan clutch is thick. That fluid is supposed to make the fan spin freely when the radiator is cool. With the engine off, and about "room" temprature, you should be able to spin the fan by hand. It won't move freely, but you should be able to move it without much effort. When the fan clutch gets hot, the bi-metal coil in the center turns, and locks the clutch together to spin the fan at engine speed. Frequently when they fail, the fan clutch will lock on at all times, no matter wat the temp.
Also, watch out for oil leaking around the shaft. Try to wobble the fan towards, and away from the radiator. I had a fan clutch fail on me about 2 years ago. The fluid leaked out, the bearing failed, and sent the fan into the radiator. What was a simple $29 became a $200 repair because I had to buy a new radiator too! Usually when this happens though, you will get some warning rattles coming from under the hood before it fails completely.
On newer Astro's with the multi-port, the fan is computer-controlled, but older ones with throttle-body injection just use the mechanical clutch I just explained
Changing a failed fan clutch
To change out the fan clutch, it involves removing one half of the fan shroud. I perfer to remove the bottom one since there are hoses and wiring in the way going through the top...not hard, just 4 bolts. There are 2 down below near the frame rails, and 2 more, clamping the two pieces together.
The fan shrouds are the only thing holding the radiator
in place, so if you see one cracked, you might want to replace it!
Since we are only removing one piece, the radiator shouldn't fall out of
place.
***By the way....If you need to change the radiator because
it's having problems too, this is a good time to do it! You just
need to drain it, disconnect the hoses, and remove the top fan shroud too.
Next, remove the serpentine belt, if you have an older model with the regular V-belts, remove the two that come across the water pump's pulley.
There are 4 bolts holding the fan assemply to the pulley, and the pulley to the water pump. Once you remove these bolts, the whole mess should slide forward right off the studs, and lower out the bottom.
The fan itself just simply bolts to the edge of the fan clutch. remove the 5 bolts holding it on, throw away the old clutch, and put the fan on the new one.
Just simply reverse the process to put everything back
together!!!