2003 GMC SONOMA radiator

When the coolant in the coolant recovery tank is at the
ADD mark, start your vehicle.
If the overheat warning continues, there’s one more
thing you can try. You can add the proper mixture
directly to the radiator, but be sure the cooling system
is cool before you do it.
{CAUTION:
Steam and scalding liquids from a hot cooling
system can blow out and burn you badly. They
are under pressure, and if you turn the radiator
pressure cap—even a little—they can come
out at high speed. Never turn the cap when the
cooling system, including the radiator pressure
cap, is hot. Wait for the cooling system and
radiator pressure cap to cool if you ever have
to turn the pressure cap.
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2003 - Sonoma OM

How to Add Coolant to the Radiator
1. You can remove the radiator pressure cap when
the cooling system, including the radiator pressure
cap and upper radiator hose, is no longer hot.
Turn the pressure cap slowly counterclockwise until
itfirst stops. (Don’t press down while turning the
pressure cap.)
If you hear a hiss, wait for that to stop. A hiss
means there is still some pressure left.2. Then keep turning the pressure cap, but now push
down as you turn it. Remove the pressure cap.
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2003 - Sonoma OM

3. Fill the radiator with the proper DEX-COOL®
coolant mixture, up to the base of thefiller
neck. SeeEngine Coolant on page 5-25for more
information about the proper coolant mixture.4. Thenfill the coolant recovery tank to ADD mark.
5. Put the cap back on the coolant recovery tank,
but leave the radiator pressure cap off.
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2003 - Sonoma OM

6. Start the engine and let it run until you can feel the
upper radiator hose getting hot. Watch out for the
engine cooling fan.
7. By this time, the coolant level inside the radiator
filler neck may be lower. If the level is lower, add
more of the proper DEX-COOL
®coolant mixture
through thefiller neck until the level reaches
the base of thefiller neck.8. Then replace the pressure cap. At any time during
this procedure if coolant begins toflow out of the
filler neck, reinstall the pressure cap. Be sure
the arrow on the pressure cap lines 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 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.
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2003 - Sonoma OM

93,000 Miles (155 000 km)
❑Change engine oil andlter (or every 3 months,
whichever occursrst).An Emission Control Service.
❑Lubricate chassis components (or every 3 months,
whichever occursrst).(See footnote #.)
❑Check rear/front axleuid level and adduid as
needed. Check constant velocity joints and axle seals
for leaking.(See footnote **.)
96,000 Miles (160 000 km)
❑Change engine oil andlter (or every 3 months,
whichever occursrst).An Emission Control Service.
❑Lubricate chassis components (or every 3 months,
whichever occursrst).(See footnote #.)
❑Check rear/front axleuid level and adduid as
needed. Check constant velocity joints and axle seals
for leaking.(See footnote **.)
❑Rotate tires. SeeTire Inspection and Rotation on
page 5-60for proper rotation pattern and additional
information.(See footnote +.)
99,000 Miles (165 000 km)
❑Change engine oil andlter (or every 3 months,
whichever occursrst).An Emission Control Service.
❑Lubricate chassis components (or every 3 months,
whichever occursrst).(See footnote #.)
❑Check rear/front axleuid level and adduid as
needed. Check constant velocity joints and axle seals
for leaking.(See footnote **.)
100,000 Miles (166 000 km)
❑Inspect spark plug wires.An Emission Control
Service.
❑Replace spark plugs.An Emission Control Service.
❑If you haven’t used your vehicle under severe service
conditions listed previously and, therefore, haven’t
changed your automatic transmissionuid, change
both theuid andlter.
Manual transmissionuid doesn’t require change.
❑4.3L V6 Engine Only: Inspect Positive Crankcase
Ventilation (PCV) valve.An Emission Control
Service.
150,000 Miles (240 000 km)
❑Drain,ush and rell cooling system (or every
60 months since last service, whichever occursrst).
SeeEngine Coolant on page 5-25for what to use.
Inspect hoses. Clean radiator, condenser, pressure
cap and neck. Pressure test cooling system and
pressure cap.An Emission Control Service.
❑Inspect engine accessory drive belt.An Emission
Control Service.
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2003 - Sonoma OM

100,000 Miles (166 000 km)
❑Inspect spark plug wires.An Emission Control
Service.
❑Replace spark plugs.An Emission Control Service.
❑If you haven’t used your vehicle under severe service
conditions listed previously and, therefore, haven’t
changed your automatic transmissionuid, change
both theuid andlter. Manual transmission
uid doesn’t require change.
❑4.3L V6 Engine Only: Inspect Positive Crankcase
Ventilation (PCV) valve.An Emission Control
Service.
150,000 Miles (240 000 km)
❑Drain,ush and rell cooling system (or every
60 months since last service, whichever occursrst).
SeeEngine Coolant on page 5-25for what to use.
Inspect hoses. Clean radiator, condenser, pressure
cap and neck. Pressure test the cooling system
and pressure cap.An Emission Control Service.
❑Inspect engine accessory drive belt.An Emission
Control Service.
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2003 - Sonoma OM

Part C: Periodic Maintenance
Inspections
Listed in this part are inspections and services which
should be performed at least twice a year (for instance,
each spring and fall).You should let your dealer’s
service department do these jobs. Make sure any
necessary repairs are completed at once.
Proper procedures to perform these services may be
found in a service manual. SeeService Publications
Ordering Information on page 7-9.
Steering, Suspension and Front
Drive Axle Boot and Seal Inspection
Inspect the front and rear suspension and steering
system for damaged, loose or missing parts, signs of
wear or lack of lubrication. Inspect the power steering
lines and hoses for proper hook-up, binding, leaks,
cracks, chang, etc. Clean and then inspect the drive
axle boot seals for damage, tears or leakage. Replace
seals if necessary.
Exhaust System Inspection
Inspect the complete exhaust system. Inspect the body
near the exhaust system. Look for broken, damaged,
missing or out-of-position parts as well as open seams,
holes, loose connections or other conditions which
could cause a heat build-up in theoor pan or could let
exhaust fumes into the vehicle. SeeEngine Exhaust
on page 2-37.
Fuel System Inspection
Inspect the complete fuel system for damage or leaks.
Engine Cooling System Inspection
Inspect the hoses and have them replaced if they
are cracked, swollen or deteriorated. Inspect all pipes,
ttings and clamps; replace as needed. Clean the
outside of the radiator and air conditioning condenser.
To help ensure proper operation, a pressure test of
the cooling system and pressure cap is recommended
at least once a year.
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2003 - Sonoma OM

Headlamps (cont.)
Halogen Bulbs............................................5-50
One-Piece Front Turn Signal Lamps...............5-52
Two-Piece Front Turn Signal Lamps...............5-53
Heated Seats................................................... 1-5
Heating.........................................................3-18
Highway Hypnosis...........................................4-34
Hill and Mountain Roads..................................4-34
Hitches..........................................................4-56
Hood
Checking Things Under.................................. 5-8
Release....................................................... 5-9
Horn ............................................................... 3-4
How to Add Coolant to the Coolant
Recovery Tank............................................5-32
How to Add Coolant to the Radiator..................5-34
How to Add Fluid....................................5-22, 5-24
How to Check................................5-20, 5-23, 5-59
How to Check and Add Fluid
............................5-25
How to Check Lubricant
..........................5-47, 5-49
How to Check Power Steering Fluid
..................5-37
How to Inspect the Engine Air Cleaner/Filter
.......5-19
How to Use This Manual
...................................... ii
How to Wear Safety Belts Properly
...................1-15
Hydraulic Clutch
.............................................5-24
Hydraulic Clutch System Check
........................6-27
Hydroplaning
..................................................4-30I
If No Steam Is Coming From Your Engine..........5-29
If Steam Is Coming From Your Engine...............5-28
If the Light Is Flashing.....................................3-30
If the Light Is On Steady.................................3-31
If You Are Stuck in Sand, Mud, Ice or Snow.......4-40
If You Do Decide To Pull A Trailer.....................4-52
If You’re Caught in a Blizzard...........................4-38
Ignition Positions.............................................2-20
Ignition Transmission Lock Check......................6-29
Infants and Young Children, Restraints...............1-32
Inflation–Tire Pressure...................................5-58
Inspection
Brake System.............................................6-32
Engine Cooling System................................6-31
Exhaust System..........................................6-31
Fuel System...............................................6-31
Part C - Periodic Maintenance.......................6-31
Steering, Suspension and Front Drive
Axle Boot and Seal..................................6-31
Throttle System...........................................6-32
Transfer Case and Front Axle
(Four-Wheel Drive)...................................6-32
Installing a Garage Door Opener.......................2-43
Instrument Panel
Cluster.......................................................3-21
Overview..................................................... 3-2
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2003 - Sonoma OM