GMC 1995 Jimmy Owner's Manual page 222

6. Start the engine
and let it run until
you can feel the
upper radiator
hose getting hot.
Watch out for the
engine fan.
7. By this time the coolant level inside the filler neck may be lower. If the
level is lower, add more of the proper mix through the filler neck until
the level reaches the base of the filler neck.
8.
Then replace the
pressure cap. At
any time during
this procedure if
coolant begins to
flow out of the
filler neck,
reinstall the
pressure cap. Be
sure the arrows
on the pressure
cap line up like
this.
Engine Fan Noise
This vehicle has a clutched engine cooling fan. When the clutch is engaged,
the fan spins faster to provide more air to cool the engine. In most every day
driving conditions the clutch is not engaged. This improves fuel economy
and reduces fan noise. Under heavy vehicle loading, trailer towing and/or
high outside temperatures, the fan speed increases when the clutch engages.
So you may hear an increase in fan noise. This is normal and should not be
mistaken as the transmission slipping or making extra shifts. It is merely the
cooling system functioning properly. The fan will slow down when
additional cooling is not required and the clutch disengages.
You may also hear this fan noise when you start the engine. It will go away
as the fan clutch disengages.
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