1999 GMC SIERRA radiator cap

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6-27 Front Axle
When to Check and Change Lubricant
Refer to the Maintenance Schedule to determine how
often to check the lubricant and when to change it. See
ªScheduled Maintenance Servicesº in the Index.
How to Check Lubricant
If the level is below the bottom of the filler plug hole,
you may need to add some lubricant.
When the differential is cold, add enough lubricant to raise
the level to 1/2 inch (12 mm) below the filler plug hole.When the differential is at operating temperature
(warm), add enough lubricant to raise the level to the
bottom of the filler plug hole.
What to Use
Refer to the Maintenance Schedule to determine what
kind of lubricant to use. See ªRecommended Fluids and
Lubricantsº in the Index.
Radiator Pressure Cap
(Gasoline Engine)

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6-28
The radiator pressure cap must be tightly installed with
the arrows on the cap lined up with the overflow tube on
the radiator filler neck.
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 AC
 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.
A 50/50 mixture of clean, drinkable water and
DEX
-COOL coolant will:

Give freezing protection down to
-34F (-37C).

Give boiling protection up to 265F (129C).

Protect against rust and corrosion.

Help keep the proper engine temperature.

Let the warning gages work as they should.

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6-31
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 -- Gasoline Engines
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7-29
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 -- Gasoline Engines
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7-40
100,000 Miles (166 000 km)

Inspect spark plug wires. An Emission Control Service.

Replace spark plugs. An Emission Control Service.

Change automatic transmission fluid and filter if the vehicle's GVWR is over
8600 lbs. or if the vehicle is mainly driven under one or more of these conditions:
± In heavy city traffic where the outside temperature regularly reaches
90
F (32
C) or higher.
± In hilly or mountainous terrain.
± When doing frequent trailer towing.
± Uses such as found in taxi, police or delivery service.
Manual transmission fluid doesn't require change.
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. Manual transmission fluid doesn't require change.
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
ACTUAL
SERVICED BY:MILEAGE
DATE

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7-46
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.

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9-8
Power
Accessory Outlet 2-59 . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Door Locks 2-6 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Driver's Seat 1-3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Option Fuses 6-70 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Remote Control Mirror 2-50 . . . . . . . . . . . . . . . . . . . . . . . .
Steering 4-9 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Steering Fluid 6-32, 7-48 . . . . . . . . . . . . . . . . . . . . . . . . . . .
Take-Off 4-61 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Winches 4-61 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Windows 2-33 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Pregnancy, Use of Safety Belts 1-22 . . . . . . . . . . . . . . . . . . . .
Problems on the Road 5-1 . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Protecting Exterior Bright Metal Parts 6-66 . . . . . . . . . . . . . . .
PTO 4-61 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Publications, Service and Owner 8-12, 8-13 . . . . . . . . . . . . . .
Radiator 5-16 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Radiator Pressure Cap 6-27 . . . . . . . . . . . . . . . . . . . . . . . . . . .
Radio Reception 3-24 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Radios 3-8 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Rain, Driving In 4-28 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Reading Lamps 2-44 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Rear
Axle 6
-25, 7-49 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Outside Seat Position 1-37, 1-41 . . . . . . . . . . . . . . . . . . . . .
Safety Belt Comfort Guides 1-43 . . . . . . . . . . . . . . . . . . . . .
Seat Passengers 1-37 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Towing 5-8 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Window Defogger 3-6 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Rear Seat 1
-7, 1-8 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Rearview Mirror 2-44 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Electrochromic Day/Night 2-45 . . . . . . . . . . . . . . . . . . . . . .
Inside Day/Night 2-44 . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Reclining Seatbacks 1-4 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Recommended Fluids and Lubricants 7-48 . . . . . . . . . . . . . . .
Recovery Hooks 5-33 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Recovery Tank, Coolant 5-11 . . . . . . . . . . . . . . . . . . . . . . . . . .
Recreational Vehicle Towing 4-41 . . . . . . . . . . . . . . . . . . . . . .
Refrigerants, Air Conditioning 6-78 . . . . . . . . . . . . . . . . . . . .
Replacement
Bulbs 6
-39, 6-75 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Parts 6-78 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Wheel 6-58 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Replacing Safety Belts 1-71 . . . . . . . . . . . . . . . . . . . . . . . . . . .
Reporting Safety Defects 8-10 . . . . . . . . . . . . . . . . . . . . . . . . .
Restraints
Checking 1
-71 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Child 1-48 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Head 1-5 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Replacing Parts After a Crash 1-71 . . . . . . . . . . . . . . . . . . .
System Check 7-42 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Right Front Passenger Position 1-23 . . . . . . . . . . . . . . . . . . . .
Roadside Assistance 8-6 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Roadside Assistance, Canadian 8-7 . . . . . . . . . . . . . . . . . . . . .
Rocking Your Vehicle 5-33 . . . . . . . . . . . . . . . . . . . . . . . . . . .
Roof Marker Lamp Bulb Replacement 6-46 . . . . . . . . . . . . . .
Rotation, Tires 6-52, 6-53 . . . . . . . . . . . . . . . . . . . . . . . . . . . .