1999 GMC YUKON radiator cap

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6-23
NOTICE:
Your radiator cap is a 15 psi (105 kPa) pressure-type
cap and must be tightly installed to prevent coolant
loss and possible engine damage from overheating.
Be sure the arrows on the cap line up with the
overflow tube on the radiator filler neck.
Thermostat
Engine coolant temperature is controlled by a thermostat
in the engine coolant system. The thermostat stops the
flow of coolant through the radiator until the coolant
reaches a preset temperature.
When you replace your thermostat, an ACDelco


thermostat is recommended.
Engine Coolant
The cooling system in your vehicle is filled with
DEX
-COOL
engine coolant. This coolant is designed
to remain in your vehicle for 5 years or 150,000 miles
(240 000 km), whichever occurs first, if you add only
DEX
-COOL
extended life coolant.
The following explains your cooling system and how to
add coolant when it is low. If you have a problem with
engine overheating, see ªEngine Overheatingº in
the Index.

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6-26
Adding Coolant
If you need more coolant, add the proper DEX
-COOL

coolant mixture at the coolant recovery tank.
CAUTION:
Turning the radiator pressure cap when the
engine and radiator are hot can allow steam and
scalding liquids to blow out and burn you badly.
With the coolant recovery tank, you will almost
never have to add coolant at the radiator.
Never turn the radiator pressure cap
-- even a
little
-- when the engine and radiator are hot.
Add coolant mixture at the recovery tank, but be careful
not to spill it.
CAUTION:
You can be burned if you spill coolant on hot
engine parts. Coolant contains ethylene glycol,
and it will burn if the engine parts are hot
enough. Don't spill coolant on a hot engine.

Short Trip/City Scheduled Maintenance
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7-24
100,000 Miles (166 000 km) (Continued)

If you haven't used your vehicle under severe service conditions listed
previously and, therefore, haven't changed your automatic transmission fluid,
change both the fluid and filter.

Inspect Positive Crankcase Ventilation (PCV) valve.
An Emission Control Service.
150,000 Miles (240 000 km)

Drain, flush and refill cooling system (or every 60 months since last service,
whichever occurs first). See ªEngine Coolantº in the Index for what to use.
Inspect hoses. Clean radiator, condenser, pressure cap and neck. Pressure test
cooling system and pressure cap.
An Emission Control Service.ACTUAL
SERVICED BY:MILEAGE
DATE

Long Trip/Highway Scheduled Maintenance
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7-34
100,000 Miles (166 000 km) (Continued)

If you haven't used your vehicle under severe service conditions listed
previously and, therefore, haven't changed your automatic transmission fluid,
change both the fluid and filter.

Inspect Positive Crankcase Ventilation (PCV) valve.
An Emission Control Service.
150,000 Miles (240 000 km)

Drain, flush and refill cooling system (or every 60 months since last service,
whichever occurs first). See ªEngine Coolantº in the Index for what to use.
Inspect hoses. Clean radiator, condenser, pressure cap and neck. Pressure test
the cooling system and pressure cap.
An Emission Control Service.ACTUAL
SERVICED BY:MILEAGE
DATE

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7-39
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 or other qualified service center 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. See ªService and Owner
Publicationsº in the Index.
Steering and Suspension 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, chafing, etc.
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 the floor pan or could let exhaust fumes into
the vehicle. See ªEngine Exhaustº in the Index.
Engine Cooling System Inspection
Inspect the hoses and have them replaced if they are
cracked, swollen or deteriorated. Inspect all pipes, fittings
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.
Throttle System Inspection
Inspect the throttle system for interference or binding,
and for damaged or missing parts. Replace parts as
needed. Replace any components that have high effort
or excessive wear. Do not lubricate accelerator and
cruise control cables.

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9-8
Radiator 5-15 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Radiator Pressure Cap 6-22 . . . . . . . . . . . . . . . . . . . . . . . . . . .
Radio Reception 3-21 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Radio 3-8 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Rain, Driving In 4-30 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Reading Lamps 2-50 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Rear
Air Conditioning and Heating Systems 3
-3 . . . . . . . . . . . . .
Axle 6-20, 7-42 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Child Security Locks 2-5 . . . . . . . . . . . . . . . . . . . . . . . . . . .
Doors 2-11 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Lamp Bulb Replacement 6-37 . . . . . . . . . . . . . . . . . . . . . . .
Outside Seat Position 1-30 . . . . . . . . . . . . . . . . . . . . . . . . . .
Safety Belt Comfort Guides 1-34 . . . . . . . . . . . . . . . . . . . . .
Seat Audio (RSA) 3-12 . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Seat Passengers 1-30 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Towing 5-8 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Window Defogger 3-7 . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Windshield Wiper and Washer 2-42 . . . . . . . . . . . . . . . . . . .
Rearview Mirror 2-51 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Rearview Mirror, Electrochromic Day/Night with
Compass/Temperature Display/Headlamp Delay 2
-51 . . . .
Rearview Mirror, Inside 2-51 . . . . . . . . . . . . . . . . . . . . . . . . . .
Reclining Front Seatbacks 1-4 . . . . . . . . . . . . . . . . . . . . . . . . .
Recovery Hooks 5-33 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Recovery Tank, Coolant 5-12 . . . . . . . . . . . . . . . . . . . . . . . . . .
Recreational Vehicle Towing 4-42 . . . . . . . . . . . . . . . . . . . . . .
Refrigerants, Air Conditioning 6-64 . . . . . . . . . . . . . . . . . . . .
Remote Compact Disc Player 3-14 . . . . . . . . . . . . . . . . . . . . . Replacement
Bulbs 6
-61, 6-62 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Parts 6-65 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Wheel 6-45 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Wheel, Used 6-46 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Replacing Safety Belts 1-57 . . . . . . . . . . . . . . . . . . . . . . . . . . .
Reporting Safety Defects 8-10 . . . . . . . . . . . . . . . . . . . . . . . . .
Restraints
Checking 1
-57 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Child 1-41 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Head 1-5, 1-7 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Replacing Parts After a Crash 1-57 . . . . . . . . . . . . . . . . . . .
System Check 7-35 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Retained Accessory Power 2-22 . . . . . . . . . . . . . . . . . . . . . . . .
Reverse, Automatic Transmission 2-26 . . . . . . . . . . . . . . . . . .
Right Front Passenger Position 1-23 . . . . . . . . . . . . . . . . . . . .
Roadside Assistance 8-6 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Roadside Assistance, Canadian 8-7 . . . . . . . . . . . . . . . . . . . . .
Rocking Your Vehicle 5-33 . . . . . . . . . . . . . . . . . . . . . . . . . . .
Rotation, Tires 6-41 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Safety Belt Extender 1-57 . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Safety Belts 1-9 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Adults 1-14 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Care 6-50 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Center Passenger Position 1-36 . . . . . . . . . . . . . . . . . . . . . .
Children 1-38 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .