1998 GMC SIERRA heater

If you get the overheat warning with no sign of steam,
try this for
a minute or so:
1. If you have an air conditioner, turn it off.
2. Turn on your heater to full hot at the highest fan
speed and open the window
as necessary.
3. If you’re in a traffic jam, shift to NEUTRAL (N);
otherwise, shift to the highest gear while
driving
-- AUTOMATIC OVERDRIVE (@)
for automatic transmissions.
If you no longer have the overheat warning, you can
drive. Just to be safe, drive slower for about
10 minutes.
If the warning doesn’t come back on, you can
drive normally.
If the warning continues, pull over, stop, and park your
vehicle right away.
If there’s still no sign
of steam, push the accelerator until
the engine speed
is about twice as fdst as normal idle
speed. Bring the engine speed back to normal idle speed
after two or three minutes. Now see if the warning stops.
But then, if you still have the warning, turn ofthe
engine
and get everyone out of the vehicle until it
cools down.
You may decide not to lift the hood but to get service
help right away.
Cooling System -- Gasoline Engines
When you decide it’s safe to lift the hood, here’s what
you’ll see:
A. Coolant Recovery Tank
B. Radiator Pressure Cap
C. Engine Fan(s)
5-15
ProCarManuals.com

If your vehicle has air conditioning, the auxiliary
electric engine cooling fan under the hood can
start up even when the engine is not running and
can injure you. Keep hands, clothing and tools
away from any underhood electric fan.
If the coolant inside the coolant recovery tank is boiling,
don’t do anything else until it cools down. The
codant level should be at or above the
COLD mark.
If it isn’t, you may have a leak in the radiator hoses,
heater hoses, radiator, water pump or somewhere else
in
the cooling system.
Heater and radiator hoses, and other engine
parts, can be very hot. Don’t touch them.
If you
do, you can be burned.
Don’t run the engine if there is a leak.
If you run
the engine, it could lose all coolant. That could
cause an engine fire, and
you could be burned.
Get any leak fixed before you drive the vehicle.
NOTICE:
Engine damage from running your engine
without coolant isn’t covered by your warranty.
ProCarManuals.com

If there seems to be no leak, start the engine again. See if
the engine cooling
fan speed increases when idle speed is
doubled
by pushing the accelerator pedal down. If it
doesn't, your vehicle needs service. Turn off the engine.
How to Add Coolant to the Coolant
Recovery Tank -- Gasoline Engines
If you haven't found a problem yet, but the coolant level
isn't at or above the COLD mark, add
a 50/50 mixture
of C'IC~LIII r.tuter- (preferably distilled) and DEX-COOL@
engine coolant at the coolant recovery tank. (See
"Engine Coolant"
in the Index for more information.)
I A CAUTION: I
I CAUTION: (Continued)
Adding only plain water to your cooling system
can be dangerous. Plain water, or some other
liquid like alcohol, can boil before the proper
coolant mix will. Your vehicle's coolant warning
system
is set for the proper coolant mix.
CAUTION: (Continued) With plain water or the wrong mix,
your engine
could get
too hot but you wouldn't get the
overheat warning. Your engine could catch
fire
and you or others could be burned. Use a 50/50
mix of clean water and DEX-COOL%oolant.
I NOTICE:
In cold weather, water can freeze and crack the
engine, radiator, heater core and other parts. Use the recommended coolant and the proper
coolant mixture.
5-17
ProCarManuals.com

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
engine coolant will require change sooner
-- at
30,000 miles (50 000 km) or 24 months,
whichever occurs first. Damage caused by the use
of coolant other than DEX-COOL@ is not
covered by your new vehicle warranty.
What to Use
Use a mixture of one-half clean water (preferably
distilled) and one-half
DEX-COOL@ coolant which
won’t damage aluminum
parts. If you use this mixture,
you don’t need to add anything else.
CAUTION:
Adding only plain water to your cooling system
can be dangerous. Plain water, or some other
liquid like alcohol, can boil before the proper
coolant mixture will. Your vehicle’s coolant
warning system is set for the proper coolant
mixture. With plain water or the wrong mixture,
your engine could get too hot but you wouldn’t
get the overheat warning. Your engine could
catch fire and you or others could be burned.
Use a
50/50 mixture of clean water and
DEX-COOL@ coolant.
6-29
ProCarManuals.com

- ~ ~~
NOTICE:
If you use an improper coolant mixture, your
engine could overheat and be badly damaged.
The repair cost wouldn’t be covered by your
warranty.
Too much water in the mixture can
freeze and crack the engine, radiator, heater core
and other parts.
If you have to add coolant more than four times a year,
have your dealer check your cooling system.
NOTICE:
If you use the proper coolant, you don’t have to
add extra inhibitors or additives which claim
to
improve the system. These can be harmful.
Checking Coolant
If your vehicle has a diesel engine, see “Checking
Coolant”
in the Diesel Engine Supplement.
,:. . .,. ..... I.. .;> .:... ...,,.. ::l:. ..
.. .
The coolant recovery tank is located on the passenger’s
side at the rear corner
of the engine compartment.
When your engine
is cold, the coolant level should be at
the
COLD mark, or a little higher. When your engine is
warm,
the level should be up to the HOT mark, or a
little higher.
6-30
ProCarManuals.com

STARTER RELAY
[-I
[-I
[T)
I BLOWER
n STOPiHAZ
Name
ECM-B RR DEFOG
IGN-E
FUEL
SOL
GLOW PLUG
Usage
Horn, Underhood Lamps
Auxiliary Fan
Injectors, PCM/VCM
Not Used
Air Conditioning
Not Used
Ignition Switch, EGR, Canister
Purge, EVRV Idle Coast Solenoid,
Heated
02, Fuel Heater
(Diesel Engine), Water Sensor
(Diesel Engine)
HTD ST-RR Not Used
LIGHTING Headlamp and Panel Dimmer
BATT Battery, Fuse Block Busbar
IGN-A Ignition Switch
IGN-B Ignition Switch Switch,
Fog and Courtesy Fuses
ABS Anti-Lock Brake Module
BLOWER High Blower Relay
STOP/HAZ Stoplamps
HEATED SEATS Not Used
6-75
Usage
Fuel Pump, PCM/VCM
Rear Window Defogger
Auxiliary Fan Relay Coi
il, AIC
Compressor Relay, Hot Fuel
Module, Dual Tanks
Fuel Solenoid (Diesel Engine)
Glow Plugs (Diesel Engine)
Name
HORN
AUX FAN
ECM- 1
HTD ST-FR
AIC HTD MIR
ENG-
1
ProCarManuals.com

Vinyl ....................................... 6-63
Wheels
..................................... 6-67
Windshield and Wiper Blades
................... 6-65
Clock. Setting the ................................ 3-7
Clutch Fluid. Hydraulic
..................... 6-25. 7-46
Clutch. System Check
........................... 7-41
Comfort Controls
................................ 3-2
Comfort Guides. Rear
........................... 1-40
Compact Disc Care
............................. 3-26
Compact Disc Player
.......................
3-16 . 3-20
Compact Disc Player Care
........................ 3-26
Compass. Rearview Mirror
with ................... 2-46
Console Storage
................................ 2-54
Control
of a Vehicle .............................. 4-5
Convex Outside Mirror .......................... 2-SO
Coolant ............................. 6-28.6-79.7-46
Heater
. Engine ............................... 2- 14
Recovery Tank ............................... 5- I5
Cooling System ................................ 5- IS
Courtesy Transportation ........................... 8-8
Cruise Control
................................. 2-38
Cupholders
.......................... 2.54.2.55. 2-56
Customer Assistance Information ................... 8- I
Customer Satisfaction Procedure .................... 8-2
Climate Control System ....................... 3.2 . 3-3
Customer Assistance for Text Telephone Users
......... 8-4
Damage. Finish
............................... 6-68
Darnage. Sheet Metal
............................ 6-67
Daytime Running Lamps
......................... 2-42
Daytime Running Lamps Indicator Lighl
............ 2-74
Dead Battery
................................... 5-3
Defects. Reporting Safety ........................ 8- 10
Defensive Driving ............................... 4-2
Defogger. Rear Window .......................... 3-6
Defoggng
and Defrosting ......................... 3-6
Dolby B Noise Reduction
....................... 3-15
Dome Lamps
.................................. 2-44
DO0
I.
Locks ....................................... 2-5
Storage Pocket ............................... 2-51
Third
........................................ 2-4
Downshifting
.................................. 2-20
Driver Position ................................. 1-14
Driving City
........................................ 4-31
Defensive
.................................... 4-2
Drunken
..................................... 4-3
Freeway
.................................... 4-32
In a Blizzard ................................. 4-38
In the Rain .................................. 4-28
Night
...................................... 4-27
Off-Road
................................... 4-14
On Curves
................................... 4-9
On Grades While Towing a Trailer ............... 4-58
On Hill and Mountain Roads .................... 4-34
On Snow and Ice
............................. 4-37
Through Water
............................... 4-30
Wet Roads
.................................. 4-28
Winte
l- ...................................... 4-36
With
a Trailer ................................ 4-56
Drunken Driving
................................ 4-3
Dual Tire Operation
............................. 6-56
9-3
ProCarManuals.com