1999 GMC SONOMA clutch

4-21 Driving Downhill
When off-roading takes you downhill, you'll want to
consider a number of things:

How steep is the downhill? Will I be able to maintain
vehicle control?

What's the surface like? Smooth? Rough? Slippery?
Hard
-packed dirt? Gravel?

Are there hidden surface obstacles? Ruts?
Logs? Boulders?

What's at the bottom of the hill? Is there a hidden
creek bank or even a river bottom with large rocks?
If you decide you can go down a hill safely, then try to
keep your vehicle headed straight down, and use a low
gear. This way, engine drag can help your brakes and
they won't have to do all the work. Descend slowly,
keeping your vehicle under control at all times.
CAUTION:
Heavy braking when going down a hill can cause
your brakes to overheat and fade. This could
cause loss of control and a serious accident.
Apply the brakes lightly when descending
a hill and use a low gear to keep vehicle speed
under control.
Q:Are there some things I should not do when
driving down a hill?
A:Yes! These are important because if you ignore them
you could lose control and have a serious accident.

When driving downhill, avoid turns that take you
across the incline of the hill. A hill that's not too
steep to drive down may be too steep to drive across.
You could roll over if you don't drive straight down.

Never go downhill with the transmission in
NEUTRAL (N), or with the clutch pedal depressed
in a manual shift. This is called ªfree
-wheeling.º
Your brakes will have to do all the work and could
overheat and fade.

5-18
Engine Fan Noise
This vehicle has a clutched engine cooling fan. When
the clutch is engaged, the fan spins faster to provide
more air to cool the engine. In most everyday driving
conditions the clutch is not engaged. This improves fuel
economy and reduces fan noise. Under heavy vehicle
loading, trailer towing and/or high outside temperatures,
the fan speed increases when the clutch engages. So you
may hear an increase in fan noise. This is normal and
should not be mistaken as the transmission slipping or
making extra shifts. It is merely the cooling system
functioning properly. The fan will slow down
when additional cooling is not required and the
clutch disengages.
You may also hear this fan noise when you start the
engine. It will go away as the fan clutch disengages.
If a Tire Goes Flat
It's unusual for a tire to ªblow outº while you're driving,
especially if you maintain your tires properly. If air goes
out of a tire, it's much more likely to leak out slowly.
But if you should ever have a ªblowout,º here are a few
tips about what to expect and what to do:
If a front tire fails, the flat tire will create a drag that
pulls the vehicle toward that side. Take your foot off the
accelerator pedal and grip the steering wheel firmly.
Steer to maintain lane position, and then gently brake to
a stop well out of the traffic lane.
A rear blowout, particularly on a curve, acts much like a
skid and may require the same correction you'd use in a
skid. In any rear blowout, remove your foot from the
accelerator pedal. Get the vehicle under control by
steering the way you want the vehicle to go. It may be
very bumpy and noisy, but you can still steer. Gently
brake to a stop
-- well off the road if possible.
If a tire goes flat, the next part shows how to use your
jacking equipment to change a flat tire safely.

6-
6-1
Section 6 Service and Appearance Care
Here you will find information about the care of your vehicle. This section begins with service and fuel information,
and then it shows how to check important fluid and lubricant levels. There is also technical information about your
vehicle, and a part devoted to its appearance care.
6
-2 Service
6
-3 Fuel (Gasoline)
6
-5 Fuel E-85 (85% Ethanol)
6
-6 Fuels in Foreign Countries
6
-7 Filling Your Tank
6
-9 Filling a Portable Fuel Container
6
-10 Checking Things Under the Hood
6
-13 Engine Oil
6
-18 Engine Air Cleaner/Filter
6
-19 Automatic Transmission Fluid
6
-23 Manual Transmission Fluid
6
-24 Hydraulic Clutch
6
-24 Rear Axle
6
-25 Four-Wheel Drive
6
-27 Engine Coolant
6
-30 Radiator Pressure Cap
6
-30 Power Steering Fluid
6
-31 Windshield Washer Fluid6
-32 Brakes
6
-36 Battery
6
-37 Bulb Replacement
6
-43 Windshield Wiper Blade Replacement
6
-45 Tires
6
-53 Appearance Care
6
-54 Cleaning the Inside of Your Vehicle
6
-56 Care of Safety Belts
6
-57 Cleaning the Outside of Your Vehicle
6
-60 GM Vehicle Care/Appearance Materials Chart
6
-61 Vehicle Identification Number (VIN)
6
-61 Service Parts Identification Label
6
-62 Electrical System
6
-67 Replacement Bulbs
6
-67 Capacities and Specifications
6
-69 Normal Maintenance Replacement Parts

6-24 How to Add Fluid
Here's how to add fluid. Refer to the Maintenance
Schedule to determine what kind of fluid to use. See
ªRecommended Fluids and Lubricantsº in the Index.
1. Remove the filler plug.
2. Add fluid at the filler plug hole. Add only enough
fluid to bring the fluid level up to the bottom of the
filler plug hole.
3. Install the filler plug. Be sure the plug is fully seated.
Hydraulic Clutch
The hydraulic clutch linkage in your vehicle is
self
-adjusting. The clutch master cylinder reservoir is
filled with hydraulic clutch fluid.
It is not necessary to regularly check clutch fluid unless
you suspect there is a leak in the system. Adding fluid
won't correct a leak.
A fluid loss in this system could indicate a problem.
Have the system inspected and repaired.
When to Check and What to Use
Refer to the Maintenance Schedule to determine how
often you should check the fluid level in your clutch
master cylinder reservoir and for the proper fluid. See
ªOwner Checks and Servicesº and ªRecommended
Fluids and Lubricantsº in the Index.
How to Check and Add Fluid
The proper fluid should be added if the level does not
reach the bottom of the diaphragm when it's in place in
the reservoir. See the instructions in the reservoir cap.
Rear 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.

6-66
Name Usage
LT TRN Left Turn Signal Rear
RT TRN Right Turn Signal Rear
RR PRK Right Rear Parking Lamps
TRL PRK Not Used
LT HDLP Left Headlamp
RT HDLP Right Headlamp
FR PRK Front Parking Lamps
INT BAT I/P Fuse Block Feed
ENG I Engine Sensors/Solenoids, MAF,
CAM, PURGE, VENT
ECM B Engine Control Module, Fuel Pump
Module, Oil Pressure
ABS Anti
-Lock Brake System
ECM I Engine Control Module Injectors
BTSI Automatic Transmission Shift Lock
Control System
B/U LP Back
-Up Lamps
A/C Air Conditioning
W/W PMP Not Used
HORN Horn
IGN B Column Feed, IGN 2, 3, 4
RAP Retained Accessory Power
LD LEV Not UsedName Usage
OXYSEN Oxygen Sensor
IGN E Engine
MIR/LKS Mirrors, Door Locks
FOG LP Fog Lamps
IGN A Starting and Charging IGN 1
STUD #2 Accessory Feeds, Electric Brake
PARKLP Parking Lamps
LR PRK Left Rear Parking Lamps
IGN C Starter Solenoid, Fuel Pump,
PRNDL
HTDSEAT Not Used
HVAC HVAC System
TRCHMSL Not Used
RRDFOG Not Used
TBC Truck Body Computer
CRANK Clutch Switch, NSBU Switch
HAZLP Hazard Lamps
VECHMSL Vehicle Center High
-Mounted
Stoplamp
HTDMIR Heated Outside Mirrors
ATC Transfer Case (Four
-Wheel Drive)
STOPLP Stoplamps
RR W/W Not Used

7-44
Automatic Transmission Check
Check the transmission fluid level; add if needed. See
ªAutomatic Transmission Fluidº in the Index. A fluid
loss may indicate a problem. Check the system and
repair if needed.
Hydraulic Clutch System Check
Check the fluid level in the clutch reservoir. See
ªHydraulic Clutch Fluidº in the Index. A fluid loss in
this system could indicate a problem. Have the system
inspected and repaired at once.
At Least Four Times a Year
Tailgate Lubrication Service
Lubricate tailgate latch bolt, handle assembly pivot points,
and hinges with lubricant recommended in Part D.
At Least Once a Year
Key Lock Cylinders Service
Lubricate the key lock cylinders with the lubricant
specified in Part D.
Body Lubrication Service
Lubricate all body door and fuel door hinges, latches
and locks including the glove box, console doors, the
body hood, secondary latch, pivots, spring anchor,
release pawl, and any moving seat hardware. Lubricate
the hood safety lever pivot and prop rod pivot. Part D
tells you what to use. More frequent lubrication may be
required when exposed to a corrosive environment.

7-45
Starter Switch Check
CAUTION:
When you are doing this check, the vehicle could
move suddenly. If it does, you or others could be
injured. Follow the steps below.
1. Before you start, be sure you have enough room
around the vehicle.
2. Firmly apply both the parking brake (see ªParking
Brakeº in the Index if necessary) and the regular brake.
NOTE: Do not use the accelerator pedal, and be
ready to turn off the engine immediately if it starts.
3. On automatic transmission vehicles, try to start the
engine in each gear. The starter should work only in
PARK (P) or NEUTRAL (N). If the starter works in
any other position, your vehicle needs service.
On manual transmission vehicles, put the shift lever
in NEUTRAL (N), push the clutch down halfway
and try to start the engine. The starter should work
only when the clutch is pushed down all the way to
the floor. If the starter works when the clutch isn't
pushed all the way down, your vehicle needs service.Automatic Transmission Shift Lock Control
System Check
CAUTION:
When you are doing this check, the vehicle could
move suddenly. If it does, you or others could be
injured. Follow the steps below.
1. Before you start, be sure you have enough
room around the vehicle. It should be parked on a
level surface.
2. Firmly apply the parking brake (see ªParking Brakeº
in the Index if necessary).
NOTE: Be ready to apply the regular brake
immediately if the vehicle begins to move.
3. With the engine off, turn the key to the RUN
position, but don't start the engine. Without applying
the regular brake, try to move the shift lever out of
PARK (P) with normal effort. If the shift lever
moves out of PARK (P), your vehicle needs service.

7-49
Part D: Recommended Fluids
and Lubricants
NOTE: Fluids and lubricants identified below by
name, part number or specification may be obtained
from your dealer.
USAGE
FLUID/LUBRICANT
Engine OilEngine Oil with the American
Petroleum Institute Certified For
Gasoline Engines starburst symbol
of the proper viscosity. To
determine the preferred viscosity
for your vehicle's engine, see
ªEngine Oilº in the Index.
Engine Coolant50/50 mixture of clean, drinkable
water and use only GM
Goodwrench

DEX-COOL
or
Havoline
DEX-COOL
Coolant.
See ªEngine Coolantº in the Index.
USAGEFLUID/LUBRICANT
Hydraulic
Brake SystemDelco Supreme 11
Brake Fluid
(GM Part No. 12377967 or
equivalent DOT
-3 Brake Fluid).
Windshield
Washer SolventGM Optikleen
Washer Solvent
(GM Part No. 1051515)
or equivalent.
Hydraulic
Clutch SystemHydraulic Clutch Fluid (GM Part
No. 12345347 or equivalent
DOT
-3 Brake Fluid).
Power
Steering SystemGM Power Steering Fluid
(GM Part No. 1052884
- 1 pint,
1050017
- 1 quart, or equivalent).
Manual
Transmission
with V6 EngineSynchromesh Transmission Fluid
(GM Part No. 12345349
or equivalent).