1986 Mercedes Benz 300E Repair Manual

The 1986 Mercedes Benz 300E is a luxury executive car featuring a 3.0L inline-6 engine, rear-wheel drive, and advanced engineering for its time. This repair manual covers essential maintenance, troubleshooting, and repair procedures for the W124 chassis platform. Below are key sections covering engine systems, transmission, electrical, brakes, suspension, and common issues.

Vehicle Specifications

Key technical data for the 1986 Mercedes Benz 300E.

Engine System

M103.983 3.0L inline-6 engine maintenance and repair procedures.

1. Oil Change: Drain plug under oil pan; use 7.5 quarts 10W-40.
2. Spark Plugs: Replace every 30,000 miles; gap 0.8mm.
3. Timing Chain: Inspect for wear at 100,000 miles.
4. Valve Adjustment: Check every 15,000 miles; adjust to 0.15mm intake, 0.30mm exhaust.

WARNING! Engine components are heavy; use proper lifting equipment. Allow engine to cool before servicing.

Transmission & Drivetrain

722.3 4-speed automatic transmission service.

1. Fluid Change: Drain and refill with 7.5 quarts Dexron II.
2. Filter Replacement: Replace transmission filter with fluid change.
3. Shift Linkage: Adjust for proper gear selection.
4. Drive Shaft: Inspect center support bearing and U-joints.

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

Electrical System

• Battery: 12V 70Ah; located in engine compartment.
• Alternator: 90A output; test voltage 13.5-14.5V.
• Starter: Direct drive type; draw current 180-220A.
• Fuse Box: Located in driver's side footwell.
• Wiring: Check for corrosion in connectors.
• Lights: Headlight adjustment screws behind housing.

Brake System

Hydraulic disc brake system maintenance.

Front Brakes: Single piston calipers, 11.0" rotors. Rear Brakes: Single piston calipers, 10.25" rotors.

Brake Pad Replacement: Remove caliper bolts, compress piston, install new pads. Brake Fluid: DOT 4; flush every 2 years. Parking Brake: Adjust cable tension at rear wheels.

Suspension & Steering

Multi-link independent suspension and recirculating ball steering.

1. Shock Absorbers: Replace in pairs; check for oil leaks.
2. Ball Joints: Inspect for play every 30,000 miles.
3. Steering Gear: Adjust lash with set screw.
4. Wheel Alignment: Camber -0.5° to +0.5°, Toe 0° to +0.2°.

Tip: Use proper spring compressors for strut replacement.

Fuel System

Bosch KE-Jetronic mechanical fuel injection system.

1. Fuel Filter: Replace every 15,000 miles; located under car.
2. Fuel Pump: Electric in-tank pump; pressure 65-75 psi.
3. Injectors: Clean every 60,000 miles.
4. Air Flow Sensor: Clean vane with electrical contact cleaner.
5. Cold Start Valve: Test for proper operation.

WARNING! Relieve fuel pressure before servicing. No smoking near fuel system.

Cooling System

Pressurized cooling system with electric fan.

1. Coolant: 50/50 mix ethylene glycol; capacity 12 quarts.
2. Thermostat: Opens at 87°C (189°F).
3. Water Pump: Replace every 60,000 miles.
4. Radiator: Flush every 2 years.
5. Fan Clutch: Check for proper engagement.

CAUTION! Never open radiator cap when hot. System operates under pressure.

Common Issues & Solutions

Frequent problems and their remedies.

Maintenance Schedule

Routine service intervals for optimal performance.

• Every 7,500 miles: Oil & filter change, tire rotation
• Every 15,000 miles: Air filter, fuel filter, valve adjustment
• Every 30,000 miles: Spark plugs, transmission fluid
• Every 60,000 miles: Coolant flush, timing chain inspection
• Every 2 years: Brake fluid flush

Troubleshooting Guide

Reset: Disconnect battery for 30 minutes to reset ECU.

Service: Contact Mercedes-Benz dealer or certified mechanic for complex issues.