lock GMC C-SERIES 1999 Workshop Manual

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5-31
1. You can remove the coolant surge tank pressure cap
when the cooling system, including the coolant surge
tank pressure cap and upper radiator hose, is no
longer hot. Turn the pressure cap slowly
counterclockwise until it first stops. (Don't press
down while turning the pressure cap.)
If you hear a hiss, wait for that to stop. A hiss means
there is still some pressure left.2. Then keep turning the cap, but now push down as
you turn it. Remove the pressure cap.
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5-35

If the wheel looks normal, see if the wheel has side
rings and a lock ring around the wheel rim. If so,
they must be seated properly. You can compare with
another wheel on the vehicle as you check for this.
For dual wheels, you have to look between the tires
to make this check. You may not be able to tell
if the side rings or lock rings are seated properly
by looking. If you can't be sure, stop and get
expert help.
CAUTION:
If you work on a pressurized tire mounted on a
damaged wheel, the assembly can expand with
explosive force without warning. You and others
nearby can be badly injured. Don't work around
a tire that has air under pressure in it when its
lock ring or side ring might not be
properly seated.
CAUTION:
Rust or dirt on the wheel, or on the parts to
which it is fastened, can make the wheel nuts
become loose after a time. The wheel could come
off and cause an accident. When you change a
wheel, remove any rust or dirt from the places
where the wheel attaches to the vehicle. In an
emergency, you can use a cloth or a paper towel
to do this; but be sure to use a scraper or wire
brush later, if you need to, to get all the rust or
dirt off.

If the lock ring and side rings seem to be seated
properly (or if the wheel doesn't have these), let the
air out of the tire. You can do this by taking out the
valve core.

If the flat or damaged tire is one of a dual set, let the
air out of both tires of the dual before you take off
the damaged tire and rim assembly.

If you have the correct equipment, put on the spare
wheel and tire assembly.
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6-7
Filling Your Tank
CAUTION:
Fuel vapor is highly flammable. It burns
violently, and that can cause very bad injuries.
Don't smoke if you're near gasoline or diesel fuel,
or if you're refueling your vehicle. Keep sparks,
flames and smoking materials away from
gasoline or diesel fuel.
The fuel cap can be on either or both sides of your
vehicle depending on option content.
To take off the cap, turn it slowly to the left
(counterclockwise).
CAUTION:
Gasoline Engine Vehicles: If you get gasoline on
you and then something ignites it, you could be
badly burned. Gasoline can spray out on you if
you open the fuel filler cap too quickly. This
spray can happen if your tank is nearly full, and
is more likely in hot weather. Open the fuel filler
cap slowly and wait for any ªhissº noise to stop.
Then unscrew the cap all the way.
When you put the cap back on, turn it to the right until
it is tight.
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6-9
Checking Things Under the Hood
To tilt the hood forward, pull out on each of the hood
latches. If the hood is equipped with hood access panels,
make sure the panel latches are locked down before
rotating the hood open.
Then take the hand holds and pull the hood forward.
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6-20
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
Maintenance Schedule.
How to Check Lubricant
If the level is below the bottom of the filler plug hole,
you'll need to add some lubricant. 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 Maintenance Schedule.
Rear Axle Shift Motor (Option)
When to Check and Change Fluid
If you have an optional air-shift two-speed, controlled
traction, or locking differential type rear axle, a good
time to check the fluid level in the axle shift motor is
when the rear axle lubricant is checked. Use refrigerant
oil (shift motor only).
How to Check Fluid
Remove the plug on the front plate of the axle shift
motor, add enough fluid to raise the level to the bottom
of the filler plug hole, then replace the plug.
What to Use
Refer to your Maintenance Schedule to determine what
kind of lubricant to use.
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6-46 Automatic Ether Injection System (Option)
If your diesel engine vehicle
has this feature, the ether
cylinder is on the upper
right rear side of the engine
compartment.
To change an empty ether cylinder, follow these steps.
1. Loosen the 5/16 inch screw head on the
cylinder
-to-bracket clamp.
2. Spread the clamp apart.3. Clean any dirt from the neck of the cylinder and the
top of the valve before you take out the cylinder.
4. Check the inside of the valve for any foreign matter.
Clean the valve as necessary.
5. Cover the valve to protect it from dirt and take out
the cylinder.
6. Install a new gasket whenever you take out the
cylinder. Use only one gasket and spread a light film
of clean oil on it before installation.
7. Put in the new cylinder. Turn it clockwise until it just
starts to contact the gasket.
8. Tighten the cylinder another half turn (180 degrees).
Don't over
-tighten.
9. Retighten the cylinder clamp.
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6-55
CAUTION:
Never use oil or grease on studs or nuts. If you
do, the nuts might come loose. Your wheel could
fall off, causing a serious accident.
Hub-Piloted Wheels, 8-Hole or 10-Hole
The studs and nuts used with these wheels have
right
-hand threads.
1. With intermittent pilot pads, position a pad at
12 o'clock to center the wheel and reduce run
-out.
2. Put the tire and rim assembly on the axle hub. Install
the outer rear tire and rim assembly so that its valve
stem is exactly opposite the valve stem on the inner
tire and rim assembly.
3. Put on the wheel nuts.
4. Finger
-tighten the nuts.
5. Oil the surfaces between
the nuts and washers as
shown. Do not oil the
studs or the threads of
the nut.
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6-68
Electrical System
Add-On Electrical Equipment
NOTICE:
Don't add anything electrical to your vehicle
unless you check with your dealer first. Some
electrical equipment can damage your vehicle
and the damage wouldn't be covered by your
warranty. Some add
-on electrical equipment can
keep other components from working as
they should.
Headlamp Wiring
The headlamp wiring is protected by a circuit breaker in
the light switch. An electrical overload will cause the
lights to go on and off, or in some cases to remain off.
If this happens, have your headlamp wiring checked
right away.
Windshield Wiper Fuses
The windshield wiper motor is protected by a circuit
breaker inside the motor and a circuit breaker in the fuse
block. If the motor overheats, the wipers will stop until
the motor cools. If the overload is caused by an
electrical problem, be sure to get it fixed.
Fusible Links
A fusible link is a short piece of wire several gage sizes
smaller than the circuit it protects. It will melt in an
overload situation, opening the circuit.
Your starter relay and other circuits have these fusible
links. The size is printed on the insulation. If the insulation
is burned beyond recognition, consult your GM dealer for
the proper size. Replace a fusible link with one of the
same size and insulation type. Fusible link insulation is a
special purpose high
-temperature material.
The hydraulic brake booster motor feed circuit and
starter relay circuit are protected by a fusible link.
Vehicles with a diesel engine have a fusible link for the
intake heater feed circuit. Vehicles equipped with an
electronically controlled diesel engine also have a
fusible link for the engine control unit.
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6-69 Power Windows and Other Power Options
Circuit breakers in the fuse panel protect the power
windows and other power accessories. When the current
load is too heavy, the circuit breaker opens and closes.
This protects the circuit until the current load returns to
normal or the problem is fixed.
Fuses and Circuit Breakers
The wiring circuits in your vehicle are protected from
short circuits by a combination of fuses, circuit breakers,
maxi
-fuses and fusible links. This greatly reduces the
chance of a fire caused by an electrical problem. There
may be a fuse taped to the wiring harness inside the
battery box and one near the generator also taped to the
wiring harness.
There are two circuit breaker/fuse blocks in your
vehicle: the instrument panel circuit breaker block and
the maxi
-fuse block.
Instrument Panel Circuit Breaker Block
This fuse block is in the lower portion of the instrument
panel, to the left of the steering column.
To open the door, pull up
and outward on the recessed
door handle and the door
will snap out.
To install the door, place the lower door into the bottom
retainer and push the top of the door in until it snaps
into place.
If you ever have a problem on the road and don't have a
spare circuit breaker, you can borrow one of the correct
value. Just pick some feature of your vehicle that you
can get along without
-- like the radio or cigarette
lighter
-- and use its circuit breaker if it is of the value
you need. Remember to replace the circuit breaker as
soon as you can.
These circuit breakers are non
-cycling; do not replace
them with cycling circuit breakers. Also, don't use
circuit breakers of higher amperage than those indicated
on the circuit breaker block.
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6-71
Name Circuits Protected
CHAS Exhaust Brake, Air Suspension
Dump Valve, Air Dryer, HYD
ABS ECHU
PARK LP Auxiliary Wiring, Air Conditioner
Controls, Parking Lamps, Turn
Signals, Taillamps, Stoplamps,
Marker Lamps, Trailer Running
Lamps, Lighted Mirrors, Radio
Receiver, Mirror Clearance Lamps
HORN Horn/Diagnostic Connector
PRK BRK Parking Brake Module
FUEL Heated Fuel Filter (Diesel
Engines) or Fuel Pump
(Gasoline Engines)
AXLE Heated Mirrors, Radiator Shutters,
Tw o
-Speed Axle Motor,
Tw o
-Speed Axle Switch
MRKR LP Roof Marker Lamps,
Trailer Marker Lamps,
Marker Lamp RelayName Circuits Protected
CIG/AUX Cigarette Lighter,
Auxiliary Power Jacks
AUX Auxiliary Wiring Relay
IGN RLY/VIN Vehicle Interface Module
(Diesel Engines) or Generator,
Coil, Injectors (Gasoline Engines)
WDO Power Windows
CRNK Starter Relay
IGN SW Instrument Panel Cluster Telltales
AUX Auxiliary Wiring
RDO Radio, Auxiliary Wiring
DR LK Power Door Locks
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