ENGINE MECHANICAL

COOLING SYSTEM TROUBLE SHOOTING

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.

COOLING SYSTEM TROUBLE SHOOTING

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

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 GASOLINE ENGINE - MECHANICAL TROUBLE SHOOTING

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.

BASIC GASOLINE ENGINE - MECHANICAL TROUBLE SHOOTING CHART
CONDITION POSSIBLE CAUSE CORRECTION

Engine Lopes At Intake manifold-to-head Replace manifold
Idle leaks gasket, See ENGINES

Blown head gasket Replace head gasket,

See ENGINES

Worn timing gears, chain Replace gears, chain or
or sprocket sprocket

Worn camshaft lobes Replace camshaft, See

ENGINES
Overheated engine Check cooling system,

See COOLING

Blocked crankcase vent Remove restriction
valve
Leaking EGR valve Repair leak and/or

replace valve
Faulty fuel pump Replace fuel pump

Engine Has Low Leaking fuel pump Repair leak and/or

Power replace fuel pump

Excessive piston-to-bore Install larger pistons,
clearance See ENGINES

Sticking valves or weak Check valve train
valve springs 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

Auto. Trans. fluid level Add fluid as necessary too low

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 Low fuel pump volume Replace fuel pump Speed Operation

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 Improper fuel pump stroke Remove pump and reset

Acceleration pump stroke

Incorrect ignition timing Reset ignition timing,

See TUNE-UP

Leaking valves Replace valves, See

ENGINES

Worn fuel pump diaphragm Replace diaphragm or

or piston piston

Intake Backfire Improper ignition timing Reset ignition timing,

See TUNE-UP

Faulty accelerator pump Replace accelerator

discharge 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 Reset choke valve

clearance too large initial clearance

Exhaust Backfire Vacuum leak Inspect and repair

vacuum system

Faulty vacuum diverter Replace vacuum diverter

valve valve

Faulty choke operation Check choke and adjust

as required

Exhaust system leak repair exhaust system

leak

Engine Ignition timing too far Reset ignition timing,

Detonation advanced See TUNE-UP

Faulty ignition system Check ignition timing,

See TUNE-UP

Spark plugs loose or Retighten or replace
faulty plugs

Fuel delivery system Inspect lines, pump and
clogged 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

Leaking, sticking or Inspect and/or replace
broken valves valves

External Oil Fuel pump improperly seated Remove pump, replace

Leakage or worn gasket gasket and seat

properly

Oil pan gasket broken or Straighten pan and

pan bent replace gasket

Timing chain cover gasket Replace timing chain

broken cover gasket

Rear main oil seal worn Replace rear main oil

seal

Oil pan drain plug not Remove and reinstall

seated properly drain plug

Camshaft bearing drain Remove restriction
hole blocked

Oil pressure sending Remove and reinstall

switch leaking sending switch

Excessive Oil Worn valve stems or guides Replace stems or
Consumption guides, See ENGINES

Valve "O" ring seals Replace "O" ring seals,

damaged See ENGINES

Plugged oil drain back holes Remove restrictions

Improper PCV valve Replace PCV valve

operation

Engine oil level too high Remove excess oil

Engine oil too thin Replace thicker oil

Valve stem oil deflectors Replace oil deflectors

damaged

Incorrect piston rings Replace piston rings,

See ENGINES

Piston ring gaps not Reinstall piston rings,
staggered See ENGINES

Insufficient piston ring Replace rings, See
tension ENGINES

Piston ring grooves or oil Replace piston rings,
return slots clogged See ENGINES
Piston rings sticking in Replace piston rings,
grooves See ENGINES

Piston ring grooves Replace piston and
excessively worn rings, See ENGINES

Compression rings installed Replace compression
upside down rings correctly, See

ENGINES

Worn or scored cylinder Rebore cylinders or
walls replace block

Mismatched oil ring Replace oil ring

expander and rail expander and rail, See

ENGINES

Intake gasket dowels too Replace intake gasket
long dowels

Excessive main or connecting Replace main or rod bearing clearance connecting rod

bearings, See ENGINES

No Oil Pressure Low oil level Add oil to proper level

Oil pressure sender or Replace sender or gauge gauge broken Oil pump malfunction Remove and overhaul oil

pump, See ENGINES

Oil pressure relief valve Remove and reinstall
sticking valve

Oil pump passages blocked Overhaul oil pump, See

ENGINES

Oil pickup screen or tube remove restriction blocked

Loose oil inlet tube Tighten oil inlet tube Loose camshaft bearings Replace camshaft

bearings, See ENGINES

Internal leakage at oil Replace block or
passages cylinder head

Low Oil Pressure Low engine oil level Add oil to proper level

Engine oil too thin Remove and replace with

thicker oil

Excessive oil pump Reduce oil pump

clearance clearance, See ENGINES

Oil pickup tube or screen Remove restrictions
blocked

Main, rod or cam bearing Replace bearing to

clearance excessive reduce clearance, See

ENGINES

High Oil Improper grade of oil Replace with proper oil

Pressure Oil pressure relief valve Eliminate binding

stuck closed

Oil pressure sender or Replace sender or gauge

gauge faulty

Noisy Main Inadequate oil supply Check oil delivery to

Bearings main bearings

Excessive main bearing Replace main bearings,

clearance See ENGINES

Excessive crankshaft end Replace crankshaft, See

play ENGINES

Loose flywheel or torque Tighten attaching bolts

converter

Loose or damaged vibration Tighten or replace

damper vibration damper

Crankshaft journals Re-grind crankshaft

out-of-round journals

Excessive belt tension Loosen belt tension

Noisy Connecting Excessive bearing clearance Replace bearing, See

Rods or missing bearing ENGINES

Crankshaft rod journal Re-grind crankshaft

out-of-round journal

Misaligned connecting rod Remove rod or cap and

or cap realign

Incorrectly tightened rod Remove and re-tighten

bolts rod bolts

Noisy Pistons Excessive piston-to-bore Install larger pistons,

and Rings clearance See ENGINES

Bore tapered or out-of-round Rebore block

Piston ring broken Replace piston rings,

See ENGINES

Piston pin loose or seized Replace piston pin, See

ENGINES

Connecting rods misaligned Realign connecting rods

Ring side clearance too Replace with larger or

loose or tight smaller rings

Carbon build-up on piston Remove carbon

Noisy Valve Worn or bent push rods Replace push rods, See

Train ENGINES

Worn rocker arms or bridged Replace push rods, See

pivots ENGINES

Dirt or chips in valve Remove lifters and

lifters remove dirt/chips

Excessive valve lifter Replace valve lifters,

leak-down See ENGINES

Valve lifter face worn Replace valve lifters,

See ENGINES

Broken or cocked valve replace or reposition

springs springs

Too much valve stem-to-guide Replace valve guides,

clearance See ENGINES

Valve bent Replace valve, See

ENGINES

Loose rocker arms Retighten rocker arms,

See ENGINES

Excessive valve seat Reface valve seats, See

run-out ENGINES

Missing valve lock Install new valve lock

Excessively worn camshaft Replace camshaft, See

lobes ENGINES

Plugged valve lifter oil Eliminate restriction

holes or replace lifter

Faulty valve lifter check Replace lifter check

ball ball, See ENGINES

Rocker arm nut installed Remove and reinstall

upside down correctly

Valve lifter incorrect for Remove and replace

engine valve lifters

Faulty push rod seat or Replace plunger or push

lifter plunger rod

Noisy Valves Improper valve lash Re-adjust valve lash,

See ENGINES Worn or dirty valve lifters Clean and/or replace

lifters
Worn valve guides Replace valve guides,

See ENGINES

Excessive valve seat or Reface seats or valve
face run-out face

Worn camshaft lobes Replace camshaft, See

ENGINES Loose rocker arm studs Re-tighten rocker arm

studs, See ENGINES
Bent push rods Replace push rods, See

ENGINES Broken valve springs Replace valve springs,

See ENGINES

Burned,Sticking Weak valve springs or Replace valves and/or

or Broken Valves warped valves springs, See ENGINES

Improper lifter clearance Re-adjust clearance or

replace lifters

Worn guides or improper Replace valve guides,

guide clearance See ENGINES

Out-of-round valve seats Re-grind valve seats

or improper seat width

Gum deposits on valve Remove deposits

stems, seats or guides

Improper spark timing Re-adjust spark timing

Broken Undersize pistons Replace with larger

Pistons/Rings pistons, See ENGINES

Wrong piston rings Replace with correct

rings, See ENGINES

Out-of-round cylinder bore Re-bore cylinder bore

Improper connecting rod Remove and realign

alignment connecting rods

Excessively worn ring Replace pistons, See

grooves ENGINES

Improperly assembled Re-assemble pin-to

piston pins -piston, See ENGINES

Insufficient ring gap Install new rings, See

clearance ENGINES

Engine overheating Check cooling system

Incorrect ignition timing Re-adjust ignition

timing, See TUNE-UP

Excessive Leaks at manifold to Replace manifold or
Exhaust Noise head, or to pipe pipe gasket

Exhaust manifold Replace exhaust

cracked or broken manifold, See ENGINES