1999 GMC SIERRA overheating

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2-69 Anti-Lock Brake System Warning Light
With the anti-lock brake
system, this light will come
on when you start your
engine and may stay on
for several seconds.
That's normal.
If the light stays on, or comes on when you're driving,
your vehicle needs service. If the regular brake system
warning light isn't on, you still have brakes, but you
don't have anti
-lock brakes. If the regular brake system
warning light is also on, you don't have anti
-lock brakes
and there's a problem with your regular brakes. See
ªBrake System Warning Lightº earlier in this section.
The anti
-lock brake system warning light should come
on briefly when you turn the ignition key to RUN. If the
light doesn't come on then, have it fixed so it will be
ready to warn you if there is a problem.
Engine Coolant Temperature Gage
This gage shows the engine
coolant temperature.
It also provides an indicator of how hard your vehicle is
working. During a majority of the operation, the gage
will read 210
F (100
C) or less. If you are pulling a
load or going up hills, it is normal for the temperature to
fluctuate and approach the 260
F (125
C) mark. If the
gage reaches the 260
F (125
C) mark, it indicates that
the cooling system is working beyond its capacity.
The ªProblems on the Road,º section of this manual
shows what to do. See ªEngine Overheatingº in
the Index.

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4-58 Driving On Grades
Reduce speed and shift to a lower gear before you start
down a long or steep downgrade. If you don't shift
down, you might have to use your brakes so much that
they would get hot and no longer work well.
If you have an automatic transmission, you can tow in
AUTOMATIC OVERDRIVE (
). You may want to
shift the transmission to THIRD (3) or, if necessary, a
lower gear selection if the transmission shifts too often
(e.g., under heavy loads and/or hilly conditions).
If you have a manual transmission and you are towing a
trailer, it's better not to use FIFTH (5) gear. Just drive in
FOURTH (4) gear (or, as you need to, a lower gear).
When towing at high altitude on steep uphill grades,
consider the following: Engine coolant will boil at a
lower temperature than at normal altitudes. If you turn
your engine off immediately after towing at high altitude
on steep uphill grades, your vehicle may show signs
similar to engine overheating. To avoid this, let the
engine run while parked (preferably on level ground)
with the automatic transmission in PARK (P) (or the
manual transmission out of gear and the parking brake
applied) for a few minutes before turning the engine off.
If you do get the overheat warning, see ªEngine
Overheatingº in the Index.
Parking on Hills
CAUTION:
You really should not park your vehicle, with a
trailer attached, on a hill. If something goes
wrong, your rig could start to move. People can
be injured, and both your vehicle and the trailer
can be damaged.
But if you ever have to park your rig on a hill, here's
how to do it:
1. Apply your regular brakes, but don't shift into
PARK (P) yet for an automatic transmission, or into
gear for a manual transmission.
2. Have someone place chocks under the trailer wheels.
3. When the wheel chocks are in place, release the
regular brakes until the chocks absorb the load.
4. Reapply the regular brakes. Then apply your
parking brake and shift into PARK (P) for an
automatic transmission, or REVERSE (R) for a
manual transmission.

5-
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5-1
Section 5 Problems on the Road
Here you'll find what to do about some problems that can occur on the road.
5
-2 Hazard Warning Flashers
5
-3 Other Warning Devices
5
-3 Jump Starting
5
-8 Towing Your Vehicle
5
-9 Engine Overheating (Gasoline Engine)5
-11 Cooling System (Gasoline Engine)
5
-19 Engine Fan Noise
5
-19 If a Tire Goes Flat
5
-20 Changing a Flat Tire
5
-32 If You're Stuck: In Sand, Mud, Ice or Snow

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5-9
Engine Overheating
(Gasoline Engine)
You will find a coolant temperature gage on your
vehicle's instrument panel. See ªEngine Coolant
Temperature Gageº in the Index.
If your vehicle has a diesel engine, see ªEngine
Overheatingº in the Diesel Engine Supplement.
If Steam Is Coming From Your Engine
CAUTION:
Steam from an overheated engine can burn you
badly, even if you just open the hood. Stay away
from the engine if you see or hear steam coming
from it. Just turn it off and get everyone away
from the vehicle until it cools down. Wait until
there is no sign of steam or coolant before you
open the hood.
If you keep driving when your engine is
overheated, the liquids in it can catch fire. You or
others could be badly burned. Stop your engine if
it overheats, and get out of the vehicle until the
engine is cool.
NOTICE:
If your engine catches fire because you keep
driving with no coolant, your vehicle can be
badly damaged. The costly repairs would not be
covered by your warranty.

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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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6-50
Tires
Your new vehicle comes with high-quality tires made by
a leading tire manufacturer. If you ever have questions
about your tire warranty and where to obtain service, see
your GM Warranty booklet for details.CAUTION:
Poorly maintained and improperly used tires
are dangerous.

Overloading your tires can cause
overheating as a result of too much friction.
You could have an air
-out and a serious
accident. See ªLoading Your Vehicleº in
the Index.

Underinflated tires pose the same danger as
overloaded tires. The resulting accident
could cause serious injury. Check all tires
frequently to maintain the recommended
pressure. Tire pressure should be checked
when your tires are cold.

Overinflated tires are more likely to be
cut, punctured or broken by a sudden
impact
-- such as when you hit a pothole.
Keep tires at the recommended pressure.

Worn, old tires can cause accidents. If your
tread is badly worn, or if your tires have
been damaged, replace them.

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9-4
Easy Entry Seat 1-6 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Electrical Equipment, Adding 2-13, 3-27, 6-69 . . . . . . . . . . .
Electrical System 6-69 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Electrochromic Day/Night Rearview Mirror 2-45 . . . . . . . . . .
Engine 6-10, 6-11 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Air Cleaner/Filter 6-17 . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Coolant 6-28, 6-76, 7-48 . . . . . . . . . . . . . . . . . . . . . . . . . . .
Coolant Heater 2-15 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Coolant Level Check 7-41 . . . . . . . . . . . . . . . . . . . . . . . . . .
Coolant Temperature Gage 2-69 . . . . . . . . . . . . . . . . . . . . .
Cooling System Capacity 6-77 . . . . . . . . . . . . . . . . . . . . . . .
Exhaust 2-31, 4-40 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Fuse Blocks 6-70, 6-73 . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Identification 6-69 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Oil Level Check 7-41 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Overheating 5-9 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Running While Parked 2-31 . . . . . . . . . . . . . . . . . . . . . . . . .
Specifications 6-76 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Starting Your 2-13 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Underhood Fuse/Relay Center 6-73 . . . . . . . . . . . . . . . . . . .
Engine Oil 6-13, 7-48 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Adding 6-14 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Additives 6-16 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Checking 6-14 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Pressure Gage 2-72 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Used 6-17 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
When to Change 6-16 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Exhaust, Engine 2-30, 4-40 . . . . . . . . . . . . . . . . . . . . . . . . . . .
Fabric Cleaning 6-61 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Fan Control, Climate Control System 3-2, 3-3 . . . . . . . . . . . .
Fender Marker Lamp Bulb Replacement 6-44 . . . . . . . . . . . . .
Filling a Portable Fuel Container 6-8 . . . . . . . . . . . . . . . . . . . .
Filling Your Tank 6-5 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Filter, Air 6-17, 6-78 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Finish Care 6-65 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Finish Damage 6-67 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Flashers, Hazard Warning 5-2 . . . . . . . . . . . . . . . . . . . . . . . . .
Flat Tire, Changing 5-20 . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Fluid Capacities 6-77 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Fluids and Lubricants 7-48 . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Foreign Countries, Fuel 6-5 . . . . . . . . . . . . . . . . . . . . . . . . . . .
Four-Wheel Drive 2-21, 6-26 . . . . . . . . . . . . . . . . . . . . . . . . .
French Language Manual ii. . . . . . . . . . . . . . . . . . . . . . . . . . .
Front Axle 6
-27, 7-49 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Front Axle Locking Feature 2-22 . . . . . . . . . . . . . . . . . . . . . . .
Front Towing 5-8 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Front Turn Signal Lamp Bulb Replacement 6-41, 6-42 . . . . .
Fuel 6-3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Filling a Portable Container 6-8 . . . . . . . . . . . . . . . . . . . . . .
Filling Your Tank 6-5 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Gage 2-75 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
In Foreign Countries 6-5 . . . . . . . . . . . . . . . . . . . . . . . . . . .
Tank Capacity 6-77 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Fuses and Circuit Breakers 6-70 . . . . . . . . . . . . . . . . . . . . . . .
Fusible Links 6-70 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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9-7
Maintenance, Underbody 6-67 . . . . . . . . . . . . . . . . . . . . . . . . .
Maintenance When Trailer Towing 4-59 . . . . . . . . . . . . . . . . .
Malfunction Indicator Lamp 2-70 . . . . . . . . . . . . . . . . . . . . . .
Manual Front Seat 1-2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Manual Mirror 2-47 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Manual Transmission
Check 7
-42 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Fluid 6-23, 7-48 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Shifting 2-19, 2-20 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Starting Your Engine 2-13 . . . . . . . . . . . . . . . . . . . . . . . . . .
Manual Windows 2-32 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Memo Pad Holder 2-54, 2-56 . . . . . . . . . . . . . . . . . . . . . . . . .
Methanol 6-4 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Mirrors 2-44 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Camper-Type 2-48 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Convex Outside 2-50 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Electrochromic Day/Night Rearview 2-45 . . . . . . . . . . . . . .
Inside Day/Night Rearview 2-44 . . . . . . . . . . . . . . . . . . . . .
Manual 2-47 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Power Remote Control 2-50 . . . . . . . . . . . . . . . . . . . . . . . . .
West Coast Type 2-49 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
MMT 6-4 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Model Reference vi. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Mountain Roads 4
-34 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
New Vehicle Break-In 2-10 . . . . . . . . . . . . . . . . . . . . . . . . . .
Night Vision 4-27 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Noise Control System 6-12 . . . . . . . . . . . . . . . . . . . . . . . . . . .
Normal Maintenance, Normal Replacement Parts 6-78 . . . . . .
Odometer 2-63 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Odometer, Trip 2-63 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Off-Road Driving 4-14 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Off-Road Recovery 4-11 . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Oil, Engine 6-13, 7-48 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Opener, Garage Door 2-51 . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Overheating Engine 5-9 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Owner Checks and Services 7-41 . . . . . . . . . . . . . . . . . . . . . . .
Owner Publications, Ordering 8-12, 8-13 . . . . . . . . . . . . . . . .
Paint Spotting, Chemical 6-67 . . . . . . . . . . . . . . . . . . . . . . . .
Park, Shifting Into 2-27 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Park, Shifting Out of 2-29 . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Parking
At Night 2
-9 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Brake 2-25 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Brake Mechanism Check 7-45 . . . . . . . . . . . . . . . . . . . . . . .
Lots 2-9 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Over Things That Burn 2-30 . . . . . . . . . . . . . . . . . . . . . . . .
With a Trailer 4-58 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Your Vehicle, Manual Transmission 2-30 . . . . . . . . . . . . . .
Passenger Position 1-23 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Passing 4-11 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Passlock
2-10, 2-73 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Periodic Maintenance Inspections 7-46 . . . . . . . . . . . . . . . . . .
Pickup Box Identification Lamp Bulb Replacement 6-46 . . . .
Pickup Conversion to Chassis Cab 4-48 . . . . . . . . . . . . . . . . .