Mitsubishi S4Q2 User Manual

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Service Manual Mitsubishi SQ-Series diesel engines
Version 08/2004
CAUSES OF ENGINE PROBLEMS AND
REMEDIES
ENGLISH
TROUBLESHOOTING
Improper fuel Poor fuel quality Drain fuel, and add high-quality fuel.
Water is mixed with fuel Drain fuel, and add high-quality fuel.
Low oil pressure Insufficient amount of oil in oil pan Add oil to specified level.
Air in oil strainer Correct damaged pipe and loose flange by replacing
parts and tightening.
Oil pump defective Disassemble and repair.
Oil lines restricted Disassemble and clean.
Relief valve defective Disassemble and inspect for damaged spring, foreign
particles on valve, and other abnormalities.
Clogged oil filter Replace filter element and oil.
Leak in oil lines Disassemble and repair.
Pumping up of oil Too much oil in oil pan Drain oil to specified level.
Worn cylinder(s), piston(s) or piston ring(s) Disassemble and repair. Replace parts.
Seizing of piston ring(s) Disassemble and repair. Replace parts.
Worn valve guide(s) Disassemble and repair. Replace parts.
Engine operated too long under no load Disassemble and repair if engine continues to
produce smoke for a while or if large amount of oil is
discharged from exhaust pipe.
Insufficient intake air Clogged air cleaner Clean or replace filter element.
Clogged intake manifold Inspect and clean.
Insufficient compression
pressure
Valve seat(s) defective Disassemble and correct.
Seizing of valve stem(s) Disassemble and correct.
Valve is pressed down by rocker Adjust valve clearance to 0.25 mm [0.0098 in.].
Worn cylinder(s), piston(s) or piston ring(s) Disassemble and repair. Replace parts.
Seizing of piston ring(s) Disassemble and repair. Replace parts.
Gas leakage from cylinder heah gasket Tighten. Replace gasket if necessary.
Damaged valve spring(s) Disassemble and replace parts.
Insufficient starter speed (at startup) Disassemble and replace parts.
Insufficient coolant Overheating Add coolant to specified level.
Water leakage from unit seal of water pump Disassemble and replace parts.
Cracks in crankcase water jacket Disassemble and replace parts.
Water leakage from other part(s) Disassemble and replace parts.
Insufficient cooling by
radiator
Inadequate air bleeding of cooling system Loosen air vent plug, drainage plug or hose clamp,
and bleed air.
Rust or water scale accumulation inside radiator Clean.
Dust accumulation on radiator Clean.
Fan belt slipping Adjust belt tension.
Thermostat defective (stuck closed) Replace parts.
Causes Details of Causes Remedies

Mitsubishi S4Q2 Specifications

General

Brand	Mitsubishi
Model	S4Q2
Category	Engine
Language	English