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