1997 GMC Sonoma Owner's Manual - Page 220

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 everyday 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 thetransmission slipping ormaking extra shifts. It is merely the cooling system functioning properly. The fan will slow down when additional cooling isnot 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. 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 expectand what to do: If a fronttire fails, the flat tire will create a dragthat pulls the vehicle toward that side. Take your foot off the accelerator pedal and grip the steering wheel firmly. Steer tomaintain lane position, and then gently brake to a stopwell 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 part shows how to use your jacking equipment to change a flat tire safely. 5-22