2000 4.7. Question of the day - r&r'd water pump last night & left engine fan off. Truck has stock efan. Do I need to put a nut on the water pump shaft to hold the pulley on? Was messing around in the shop waiting for efan to kick on, truck getting hotter & hotter and it wouldn't come on, coolant boiling out of filler neck. Thought I was going to have to put the viscous fan back on. Put radiator cap back on and viola!, fan came on. Must be a pressure switch to turn that on too. Drove home 30 miles & seems like all is fine. But anyways, do I need to put a nut on the pump shaft?

 

The e-fan supplements the engine driven fan for when the a/c (or defrost) is running or if the engine begins to overheat. There is no "pressure switch" just temperature.

If you drive in stop/go traffic, tow a lot, or run in very hot conditions your electric fan won't cut it. Remember too, you have a 4.7 and they do not like to get hot.

You can change over to another style e-fan with a proper controller but that's not what the OEM fan was designed to do.

That you saw coolant boiling, and it will without a cap on, is not a good sign. The system is designed to run under pressure to raise the boiling point. Water can boil in the engine and then it isn't cooling as effectively - hot spots result and heads can warp.

To bleed the air out you fill the system and put the cap on. Start it, run it at 3000 rpm for 10 seconds, then top it off - DONE.

Right from the FSM:

REFILLING 4.7L ENGINE
CAUTION: Failure to follow the procedure outlined below, can result in engine overheating conditions and severe damage to engine.
(1) Tighten the radiator draincock and the cylinder block drain plug(s) (if removed).
(2) Fill system using a 50/50 mixture of ethyleneglycol antifreeze and low mineral content water.
(3) Fill coolant reservoir to FULL mark.
(4) Install radiator cap and reservoir cap.
(5) Start engine and run at 3000 RPM for 10 seconds.
(6) Shut engine off.
(7) Remove radiator cap.
(8) Fill radiator to full level.
(9) Install the radiator cap

 

Live in rural North Dakota, no stop an go traffic, very little towing, and it gets hot outside about 2 days a year in july. Will give it a try with just the e fan. What about my original question, needing a nut on the water pump shaft?

 

No, you don't need a nut on your water pump shaft, that screwed nipple is just for attaching the clutch. The pulley will stay on without the clutch being attached. I would follow 00DakDan's advice and put the fan and clutch back on . If not, just plan for every situation where you might be sitting idling for a long period of time, traffic accident, warming up in the morning, etc..Also you can make the efan come on by turning to "defrost" and turning your heater fan "on", this might help if you get caught idling/running hot and need the efan. good luck!

 

Some good information- http://hellafunctional.com/?p=629 and http://www.engineeringtoolbox.com/bo...ter-d_926.html

http://docs.engineeringtoolbox.com/d...emperature.pdf

atmospheric air is about 14 PSIA, which is what a raw data of your MAP sensor will give you with key on/engine off. Pure water boils at 212F at 14PSIA and 246F at 28 PSIA. Pure anti-freeze freezes at 10 degrees F and boils at 350F at 14PSIA. Because of the specific heat properties, the industry has settled on 40/60 to 60/40 for acceptable combination ranges.

Now keep in mind that most of our trucks come with 195F thermostats....