Enginefannoise; If A Tire Goes Flat - GMC 1994 Yukon Owner's Manual

Engine Fan Noise
Your 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 fan is spinning slower and clutch is not fully engaged.
This improves fuel economy and reduces fan noise. Under heavy vehicle
loading, trailer towing and/or high outside temperatures, the fan speed
increases as the clutch more fully 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 partially disengages.
You may also hear this fan noise when you start the engine. It will go away
as the fan clutch partially disengages.
If a Tire Goes Flat
It's unusual for a tire to "blow out" while you're driving, especially if you
maintain your tires properly. If air goes out of a tire, it's much more likely to
leak out slowly. But if you should ever have a "blowout," here are a few tips
about what to expect and what to do:
If
a front tire fails, the flat tire will create a drag that pulls the vehicle
toward that side. Take your foot off the accelerator pedal and grip the
steering wheel firmly. Steer to maintain lane position, then gently brake to a
stop well out of the traffic lane.
A rear blowout, particularly on a curve, acts much like a skid and may
require the same correction you'd use in a skid. In any rear blowout, remove
your foot from the accelerator pedal. Get the vehicle under control by
steering the way you want the vehicle to go. It may be very bumpy and
noisy, but you can still steer. Gently brake to a stop, well off the road if
possible.
If a tire goes flat, the next section shows how to use your jacking equipment
to change a flat tire safely.
5-24