Hummer H2. Instruction - page 25

ENGINE MECHANICAL

COOLING SYSTEM TROUBLE SHOOTING

COOLING SYSTEM TROUBLE SHOOTING

Uneven pad wear caused by caliper

See DISC BRAKES or BRAKE SYSTEM

Uneven rotor wear

See DISC BRAKES or BRAKE SYSTEM

Drums out-of-round

Reface or replace drums

NOTE:

This is GENERAL information. This article is not intended to be specific to any
unique situation or individual vehicle configuration. The purpose of this Trouble
Shooting information is to provide a list of common causes to problem
symptoms. For model-specific Trouble Shooting, refer to SUBJECT,
DIAGNOSTIC, or TESTING articles available in the section(s) you are accessing.

CONDITION & POSSIBLE CAUSE

CORRECTION

Overheating

Coolant Leak

Fill/Pressure Test System

A/C Condenser Fins Clogged

Remove/Clean Condenser

Radiator Fins Clogged

Remove/Clean Radiator

Thermostat Stuck Closed

Replace Thermostat

Clogged Cooling System Passages

Clean/Flush Cooling System

Water Pump Malfunction

Replace Water Pump

Fan Clutch Malfunction

Replace Fan Clutch

Retarded Ignition Timing

Reset Ignition Timing

Cooling Fan Malfunction

Test Cooling Fan/Circuit

Cooling Fan Motor Malfunction

Test Fan Motor

Cooling Fan Relay Malfunction

Test Fan Relay

Faulty Radiator Cap

Replace Radiator Cap

Broken/Slipping Fan Belt

Replace Fan Belt

Restricted Exhaust

Repair Exhaust System

Corrosion

Impurities In Coolant

Clean/Flush System

Coolant Leakage

Damaged hose

Replace Hose

Leaky Water Pump

Replace Water Pump

Damaged Radiator Seam

Replace/Repair Radiator

Leaky Thermostat Cover

Replace Thermostat Cover

Cylinder Head Problem

Check Head/Head Gasket

Leaky Freeze Plugs

Replace Freeze Plugs

1998 Chevrolet Pickup C1500

GENERAL INFORMATION Trouble Shooting - Basic Procedures

GASOLINE ENGINE - MECHANICAL TROUBLE SHOOTING

BASIC GASOLINE ENGINE - MECHANICAL TROUBLE SHOOTING CHART

Recovery System Inoperative

Loose and/or Defective Radiator Cap

Replace Radiator Cap

Overflow Tube Clogged and/or Leaking

Repair Tube

Recovery Bottle Vent Restricted

Clean Vent

No Heater Core Flow

Collapsed Heater Hose

Replace Heater Hose

Plugged Heater Core

Clean/Replace Heater Core

Faulty Heater Valve

Replace Heater Valve

NOTE:

This is GENERAL information. This article is not intended to be specific to any
unique situation or individual vehicle configuration. The purpose of this Trouble
Shooting information is to provide a list of common causes to problem
symptoms. For model-specific Trouble Shooting, refer to SUBJECT,
DIAGNOSTIC, or TESTING articles available in the section(s) you are accessing.

CONDITION & POSSIBLE CAUSE

CORRECTION

Engine Lopes At Idle

Intake manifold-to-head leaks

Replace manifold gasket, See ENGINES

Blown head gasket

Replace head gasket, See ENGINES

Worn timing gears, chain or sprocket

Replace gears, chain or sprocket

Worn camshaft lobes

Replace camshaft, See ENGINES

Overheated engine

Check cooling system, See COOLING

Blocked crankcase vent valve

Remove restriction

Leaking EGR valve

Repair leak and/or replace valve

Faulty fuel pump

Replace fuel pump

Engine Has Low Power

Leaking fuel pump

Repair leak and/or replace fuel pump

Excessive piston-to-bore clearance

Install larger pistons, See ENGINES

Sticking valves or weak valve springs

Check valve train components, See

ENGINES

Incorrect valve timing

Reset valve timing, See ENGINES

Worn camshaft lobes

Replace camshaft, See ENGINES

Blown head gasket

Replace head gasket. See ENGINES.

Clutch slipping

Adjust pedal and/or replace components, See

ENGINES

Engine overheating

Check cooling system, See COOLING

Auto. Trans. pressure regulator valve
faulty

Replace pressure regulator valve

1998 Chevrolet Pickup C1500

GENERAL INFORMATION Trouble Shooting - Basic Procedures

Auto. Trans. fluid level too low

Add fluid as necessary

Improper vacuum diverter valve
operation

Replace vacuum diverter valve

Vacuum leaks

Inspect vacuum system and repair as

required

Leaking piston rings

Replace piston rings, See ENGINES

Faulty High Speed Operation

Low fuel pump volume

Replace fuel pump

Leaking valves or worn

Replace valves and/or springs, See

ENGINES

Incorrect valve timing

Reset valve timing,See ENGINES

Intake manifold restricted

Remove restriction

Worn distributor shaft

Replace distributor

Faulty Acceleration

Improper fuel pump stroke

Remove pump and reset pump stroke

Incorrect ignition timing

Reset ignition timing, See TUNE-UP

Leaking valves

Replace valves, See ENGINES

Worn fuel pump diaphragm or piston

Replace diaphragm or piston

Intake Backfire

Improper ignition timing

Reset ignition timing, See TUNE-UP

Faulty accelerator pump discharge

Replace accelerator pump

Improper choke operation

Check choke and adjust as required

Defective EGR valve

Replace EGR valve

Fuel mixture too lean

Reset air/fuel mixture, See TUNE-UP

Choke valve initial clearance too large

Reset choke valve initial clearance

Exhaust Backfire

Vacuum leak

Inspect and repair vacuum system

Faulty vacuum diverter valve

Replace vacuum diverter valve

Faulty choke operation

Check choke and adjust as required

Exhaust system leak

repair exhaust system leak

Engine Detonation

Ignition timing too far advanced

Reset ignition timing, See TUNE-UP

Faulty ignition system

Check ignition timing, See TUNE-UP

Spark plugs loose or faulty

Retighten or replace plugs

Fuel delivery system clogged

Inspect lines, pump and filter for clog

EGR valve inoperative

Replace EGR valve

PCV system inoperative

Inspect and/or replace hoses or valve

Vacuum leaks

Check vacuum system and repair leaks

Excessive combustion chamber deposits

Remove built-up deposits

1998 Chevrolet Pickup C1500

GENERAL INFORMATION Trouble Shooting - Basic Procedures

Leaking, sticking or broken valves

Inspect and/or replace valves

External Oil Leakage

Fuel pump improperly seated or worn
gasket

Remove pump, replace gasket and seat

properly

Oil pan gasket broken or pan bent

Straighten pan and replace gasket

Timing chain cover gasket broken

Replace timing chain cover gasket

Rear main oil seal worn

Replace rear main oil seal

Oil pan drain plug not seated properly

Remove and reinstall drain plug

Camshaft bearing drain hole blocked

Remove restriction

Oil pressure sending switch leaking

Remove and reinstall sending switch

Excessive Oil Consumption

Worn valve stems or guides

Replace stems or guides, See ENGINES

Valve "O" ring seals damaged

Replace "O" ring seals, See ENGINES

Plugged oil drain back holes

Remove restrictions

Improper PCV valve operation

Replace PCV valve

Engine oil level too high

Remove excess oil

Engine oil too thin

Replace thicker oil

Valve stem oil deflectors damaged

Replace oil deflectors

Incorrect piston rings

Replace piston rings, See ENGINES

Piston ring gaps not staggered

Reinstall piston rings, See ENGINES

Insufficient piston ring tension

Replace rings, See ENGINES

Piston ring grooves or oil return

slots clogged Replace piston rings, See

ENGINES

Piston rings sticking in grooves

Replace piston rings, See ENGINES

Piston ring grooves excessively worn

Replace piston and rings, See ENGINES

Compression rings installed upside
down

Replace compression rings correctly, See

ENGINES

Worn or scored cylinder walls

Rebore cylinders or replace block

Mismatched oil ring expander and rail

Replace oil ring expander and rail, See

ENGINES

Intake gasket dowels too long

Replace intake gasket dowels

Excessive main or connecting rod
bearing clearance

Replace main or connecting rod bearings,

See ENGINES

No Oil Pressure

Low oil level

Add oil to proper level

Oil pressure sender or gauge broken

Replace sender or gauge

Oil pump malfunction

Remove and overhaul oil pump, See

ENGINES

Oil pressure relief valve sticking

Remove and reinstall valve

Oil pump passages blocked

Overhaul oil pump, See ENGINES

1998 Chevrolet Pickup C1500

GENERAL INFORMATION Trouble Shooting - Basic Procedures

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