1988 Mercedes Benz 300E Repair Manual

The 1988 Mercedes Benz 300E is a luxury executive sedan featuring a 3.0L inline-6 M103 engine, rear-wheel drive, 4-speed automatic transmission, advanced suspension system, and comprehensive electronic systems. This repair manual covers essential maintenance procedures, troubleshooting guides, and technical specifications for proper servicing and repair of all major components including engine, transmission, brakes, suspension, electrical systems, and bodywork.

1. Vehicle Specifications 2. Engine System 3. Transmission & Drivetrain 4. Braking System 5. Suspension & Steering 6. Electrical System 7. Fuel System 8. Cooling System 9. Body & Interior 10. Maintenance Schedule 11. Troubleshooting Guide

Vehicle Specifications

Technical specifications and general vehicle data for the 1988 Mercedes Benz 300E.

Specification	Details
Engine Type	M103.980 3.0L inline-6
Displacement	2962 cc
Power Output	177 hp @ 5700 rpm
Torque	188 lb-ft @ 4400 rpm
Transmission	4-speed automatic (722.3)
Drivetrain	Rear-wheel drive
Fuel System	CIS-E electronic fuel injection
Brakes	Front disc, rear disc with ABS
Suspension	Independent front and rear
Curb Weight	3,285 lbs

Engine System

Complete engine maintenance and repair procedures for the M103 inline-6 engine.

Oil change procedure: Drain oil, replace filter (Mann HU 816/1x), refill with 7.5 quarts 10W-40.
Spark plug replacement: Bosch WR9DC, gap 0.8mm, torque 18-22 ft-lbs.
Timing chain inspection: Check tensioner and chain wear every 60,000 miles.
Valve adjustment: Hydraulic lifters, no adjustment required.
Compression test: Normal range 150-175 psi, max variation 15 psi.

WARNING! Always disconnect battery before working on engine electrical components. Allow engine to cool before servicing.

Transmission & Drivetrain

Automatic transmission service and drivetrain maintenance procedures.

Transmission fluid change: Drain and refill with 7.5 quarts Dexron II.
Filter replacement: Replace transmission filter every 30,000 miles.
Drive shaft inspection: Check U-joints and center support bearing.
Differential service: Replace gear oil every 60,000 miles.
Transmission mount inspection: Check for wear and deterioration.

CAUTION! Use only specified transmission fluid. Overfilling can cause damage.

Braking System

Brake system maintenance, repair, and ABS troubleshooting.

Front Brakes: 11.0-inch ventilated discs, single-piston calipers.
Rear Brakes: 10.9-inch solid discs, single-piston calipers.
ABS System: Bosch ABS 2 system with wheel sensors.
Brake Fluid: DOT 4, replace every 2 years.
Pad Replacement: Front pads last 30,000-45,000 miles.

Suspension & Steering

Suspension components and steering system service procedures.

Front Suspension: Double wishbone with gas-charged shocks and stabilizer bar. Rear Suspension: Multi-link independent with level control. Steering: Recirculating ball with power assist.

Common repairs: Ball joint replacement, shock absorber replacement, alignment specifications (camber: -0.5° to +0.5°, toe: 0° to +0.2°), steering gear adjustment.

Electrical System

Electrical system diagnosis and repair for all components.

Battery: 12V 70Ah, located in engine compartment.
Alternator: 80A output, test voltage 13.5-14.5V.
Starter: 1.4kW, check solenoid and brushes.
Fuse box: Located in engine compartment and driver's side kick panel.
Lighting: Headlight adjustment and bulb replacement procedures.

Tip: Always use Mercedes-specific diagnostic procedures for electrical troubleshooting.

Fuel System

CIS-E continuous injection system maintenance and repair.

Fuel pump: Electric in-tank pump, pressure 65-75 psi.
Fuel filter: Replace every 15,000 miles.
Injectors: Clean every 30,000 miles.
Air flow sensor: Check and clean vane assembly.
Fuel pressure regulator: Test and replace if leaking.

WARNING! Relieve fuel pressure before servicing fuel system components.

Cooling System

Cooling system maintenance and radiator service procedures.

Coolant capacity: 11.5 quarts (50/50 mix). Thermostat: Opens at 87°C. Radiator: Aluminum core with plastic tanks. Cooling fan: Viscous clutch type.

Service procedures: Flush system every 2 years, check fan clutch operation, inspect hoses and belts, pressure test system.

Body & Interior

Body panel repair and interior component service.

Door adjustment, window regulator replacement, seat mechanism repair, dashboard component removal, trim panel installation procedures.

Maintenance Schedule

Recommended maintenance intervals for optimal performance.

Service	Interval	Procedure
Oil Change	7,500 miles	Replace oil and filter
Air Filter	15,000 miles	Replace paper element
Spark Plugs	30,000 miles	Replace and gap properly
Timing Chain	60,000 miles	Inspect for wear
Coolant	2 years	Complete system flush

Troubleshooting Guide

Common problems and solutions for the 1988 Mercedes Benz 300E.

Symptom	Possible Cause	Corrective Action
Hard starting	Fuel pressure, ignition	Check fuel pump pressure, test spark plugs and wires
Rough idle	Vacuum leaks, sensors	Inspect vacuum hoses, test oxygen sensor
Transmission slipping	Low fluid, worn bands	Check fluid level and condition, adjust bands
ABS light on	Wheel sensors	Test wheel speed sensors, check wiring
Overheating	Coolant, thermostat	Check coolant level, test thermostat operation

Diagnostic: Use factory diagnostic port for code retrieval.

Service Support: Contact Mercedes-Benz technical support for complex issues.