1999 CHEVROLET TAHOE overheating

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2-76 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 (160
C) mark. If the
gage reaches the 260
F (160
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.
Malfunction Indicator Lamp (Service
Engine Soon Light) (Gasoline Engine)
Your vehicle is equipped
with a computer which
monitors operation of the
fuel, ignition and emission
control systems.
This system is called OBD II (On
-Board
Diagnostics
-Second Generation) and is intended to
assure that emissions are at acceptable levels for the life
of the vehicle, helping to produce a cleaner
environment. The SERVICE ENGINE SOON light
comes on to indicate that there is a problem and service
is required. Malfunctions often will be indicated by the
system before any problem is apparent. This may
prevent more serious damage to your vehicle. This
system is also designed to assist your service technician
in correctly diagnosing any malfunction.

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4-54 Making Turns
NOTICE:
Making very sharp turns while trailering could
cause the trailer to come in contact with the
vehicle. Your vehicle could be damaged. Avoid
making very sharp turns while trailering.
When you're turning with a trailer, make wider turns than
normal. Do this so your trailer won't strike soft shoulders,
curbs, road signs, trees or other objects. Avoid jerky or
sudden maneuvers. Signal well in advance.
Turn Signals When Towing a Trailer
The arrows on your instrument panel will flash
whenever you signal a turn or lane change. Properly
hooked up, the trailer lamps will also flash, telling other
drivers you're about to turn, change lanes or stop.
When towing a trailer, the arrows on your instrument panel
will flash for turns even if the bulbs on the trailer are burned
out. Thus, you may think drivers behind you are seeing your
signal when they are not. It's important to check occasionally
to be sure the trailer bulbs are still working.
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.
You should 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).
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) for a few
minutes before turning the engine off. If you do get the
overheat warning, see ªEngine Overheatingº in
the Index.

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
-2 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
-36 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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6-25
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.
NOTICE:
When adding coolant, it is important that you use
only DEX
-COOL (silicate-free) coolant. If
coolant other than DEX
-COOL is added to the
system, premature engine, heater core or
radiator corrosion may result. In addition, the
NOTICE: (Continued)

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6-43
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.
CAUTION: (Continued)
CAUTION: (Continued)

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.
Inflation -- Tire Pressure
The Certification/Tire label, which is on the rear edge of
the driver's door, or on the incomplete vehicle document
in the cab, shows the correct inflation pressures for your
tires when they're cold. ªColdº means your vehicle has
been sitting for at least three hours or driven no more
than 1 mile (1.6 km).
You can operate some vehicles at reduced inflation
pressures only when you'll be carrying reduced loads. On
those vehicles, the minimum cold inflation pressures for a
typical reduced load are printed on the Improved Ride Tire
Pressure label located on the driver's door. Weigh the
vehicle to find the load on each tire and see the label for
the minimum cold inflation pressures for that load.

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9-4
Easy Entry Seat (2-Door Utility) 1-7 . . . . . . . . . . . . . . . . . . .
Electric Tailgate Glass Release 2-33 . . . . . . . . . . . . . . . . . . . .
Electrical Equipment, Adding 2-14, 3-27, 6-60 . . . . . . . . . . .
Electrical System 6-60 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Electrochromic Day/Night Rearview
Mirror with Compass 2
-43 . . . . . . . . . . . . . . . . . . . . . . . . . . .
Electrochromic Day/Night Rearview
Mirror with Compass/Temperature Display 2
-47 . . . . . . . . .
Electrochromic Outside Rearview Mirrors 2-52, 3-9 . . . . . . .
Electronic Compass 2-43, 2-47 . . . . . . . . . . . . . . . . . . . . . . . .
Engine 6-10, 6-11 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Coolant 6-25, 7-44 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Coolant Heater 2-15 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Coolant Level Check 7-38 . . . . . . . . . . . . . . . . . . . . . . . . . .
Coolant Temperature Gage 2-76 . . . . . . . . . . . . . . . . . . . . .
Cooling System 6-68 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Exhaust 2-29, 4-41 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Identification 6-59 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Oil Level Check 7-38 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Overheating 5-9 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Running While Parked 2-30 . . . . . . . . . . . . . . . . . . . . . . . . .
Specifications 6-67 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Starting Your 2-13 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Engine Oil 6-12, 6-69, 7-44 . . . . . . . . . . . . . . . . . . . . . . . . . .
Adding 6-13 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Additives 6-15 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Checking 6-13 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Pressure Gage 2-79 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Used 6-16 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
When to Change 6-15 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Entry to the Rear Seat (Suburban Second Seat) 1
-11 . . . . . . . .
Ethanol 6-4 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Exhaust, Engine 2-29, 4-41 . . . . . . . . . . . . . . . . . . . . . . . . . . .
Exterior Lamps 2-40 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Fabric Cleaning 6-51 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Filling a Portable Fuel Container 6-8 . . . . . . . . . . . . . . . . . . . .
Filling Your Tank 6-5 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Filter, Air 6-16, 6-68 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Filter, Engine Oil 6-15, 6-68 . . . . . . . . . . . . . . . . . . . . . . . . . .
Finish Care 6-55 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Finish Damage 6-57 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
First Gear, Automatic Transmission 2-18 . . . . . . . . . . . . . . . .
Flashers, Hazard Warning 5-2 . . . . . . . . . . . . . . . . . . . . . . . . .
Flat Tire, Changing 5-19 . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Fluid Capacities 6-68 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Fluid Leak Check 6-34 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Fluids and Lubricants 7-44 . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Folding the Rear Seat (2-Door Utility) 1-8 . . . . . . . . . . . . . . .
Folding the Rear Seat (4-Door Models) 1-10 . . . . . . . . . . . . .
Foreign Countries, Fuel 6-5 . . . . . . . . . . . . . . . . . . . . . . . . . . .
Four-Wheel Drive 2-19, 6-22 . . . . . . . . . . . . . . . . . . . . . . . . .
French Language Manual ii. . . . . . . . . . . . . . . . . . . . . . . . . . .
Front Axle 6
-24, 7-45 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Front Axle Locking Feature 2-19 . . . . . . . . . . . . . . . . . . . . . . .
Front Park/Turn Signal Bulb Replacement 6-38, 6-39 . . . . . .
Front Sidemarker Lamp Bulb Replacement 6-40 . . . . . . . . . . .
Front Towing 5-8 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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9-7
Maintenance Schedule 7-1 . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Long Trip/Highway Definition 7-6 . . . . . . . . . . . . . . . . . . .
Long Trip/Highway Intervals 7-7 . . . . . . . . . . . . . . . . . . . . .
Owner Checks and Services 7-38 . . . . . . . . . . . . . . . . . . . . .
Periodic Maintenance Inspections 7-42 . . . . . . . . . . . . . . . .
Recommended Fluids and Lubricants 7-44 . . . . . . . . . . . . .
Scheduled Maintenance Services 7-4 . . . . . . . . . . . . . . . . . .
Short Trip/City Definition 7-5 . . . . . . . . . . . . . . . . . . . . . . .
Short Trip/City Intervals 7-5 . . . . . . . . . . . . . . . . . . . . . . . .
Maintenance, Underbody 6-57 . . . . . . . . . . . . . . . . . . . . . . . . .
Maintenance When Trailer Towing 4-56 . . . . . . . . . . . . . . . . .
Malfunction Indicator Lamp 2-76 . . . . . . . . . . . . . . . . . . . . . .
Manual Front Seat 1-2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Manual Mirror 2-50 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Manual Windows 2-31 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Methanol 6-4 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Mirrors 2-43 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Camper Type 2-50 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Convex Outside 2-52 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Electrochromic Day/Night Rearview with Compass 2-43 . .
Electrochromic Day/Night Rearview with
Compass/Temperature Display 2
-47 . . . . . . . . . . . . . . . . .
Electrochromic Outside Rearview 2-52, 3-9 . . . . . . . . . . . .
Inside Rearview 2-43, 2-47 . . . . . . . . . . . . . . . . . . . . . . . . .
Manual 2-50 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Power Remote Control 2-52 . . . . . . . . . . . . . . . . . . . . . . . . .
MMT 6-4 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Model Reference vi. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Mountain Roads 4
-36 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Multifunction Lever 2-34 . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Neutral, Automatic Transmission 2-17 . . . . . . . . . . . . . . . . .
New Vehicle Break-In 2-12 . . . . . . . . . . . . . . . . . . . . . . . . . . .
Night Vision 4-29 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Normal Maintenance Replacement Parts 6-69 . . . . . . . . . . . . .
Odometer 2-71 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Odometer, Trip 2-71 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Off-Road Driving 4-14 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Off-Road Recovery 4-11 . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Oil, Engine 6-12, 6-69, 7-44 . . . . . . . . . . . . . . . . . . . . . . . . . .
Opener, Garage Door 2-53 . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Overdrive, Automatic Transmission 2-18 . . . . . . . . . . . . . . . .
Overheating Engine 5-9 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Owner Checks and Services 7-38 . . . . . . . . . . . . . . . . . . . . . . .
Owner Publications, Ordering 8-11, 8-12 . . . . . . . . . . . . . . . .
Paint Spotting, Chemical 6-57 . . . . . . . . . . . . . . . . . . . . . . . .
Park
Automatic Transmission 2
-16 . . . . . . . . . . . . . . . . . . . . . . .
Shifting Into 2-26 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Shifting Out of 2-28 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Parking
At Night 2
-11 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Brake 2-25 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Brake Mechanism Check 7-41 . . . . . . . . . . . . . . . . . . . . . . .
Lots 2-11 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Over Things That Burn 2-29 . . . . . . . . . . . . . . . . . . . . . . . .
With a Trailer 4-55 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Passenger Position 1-29 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .