1987 Mercedes Benz 420SEL Repair Manual

The 1987 Mercedes Benz 420SEL is a luxury sedan featuring a 4.2L V8 engine, rear-wheel drive, and advanced engineering for its time. This repair manual covers comprehensive maintenance, troubleshooting, and repair procedures for engine, transmission, electrical systems, suspension, brakes, and interior components. Below are key sections for specifications, maintenance schedules, repair procedures, troubleshooting, and technical data.

1. Vehicle Specifications 2. Maintenance Schedule 3. Engine System 4. Transmission & Drivetrain 5. Electrical System 6. Suspension & Steering 7. Brake System 8. Interior & Body 9. Troubleshooting Guide 10. Technical Data 11. Safety Precautions

Vehicle Specifications

Key technical details: 4.2L V8 engine, 4-speed automatic transmission, luxury sedan body style.

Specification	Details
Engine Type	4.2L V8 M116/M117 gasoline engine
Horsepower	201 hp @ 5200 rpm
Torque	228 lb-ft @ 3500 rpm
Transmission	4-speed automatic 4G-TRONIC
Fuel System	Bosch KE-Jetronic fuel injection
Brakes	Front disc, rear disc with ABS
Suspension	Independent front and rear with self-leveling
Wheelbase	121.1 inches
Length	202.7 inches
Weight	3,770 lbs

Maintenance Schedule

Regular maintenance intervals for optimal performance and longevity.

Oil Change: Every 7,500 miles or 12 months
Spark Plugs: Every 30,000 miles
Air Filter: Every 15,000 miles
Timing Chain: Inspect every 60,000 miles
Brake Fluid: Replace every 2 years
Coolant: Replace every 3 years or 30,000 miles

WARNING! Use only Mercedes-Benz approved fluids and parts. Follow torque specifications precisely.

Engine System

4.2L V8 engine repair and maintenance procedures.

Spark Plug Replacement: Remove ignition wires, replace plugs with proper gap
Fuel Filter: Locate near fuel tank, depressurize system before replacement
Timing Chain: Requires special tools for proper tension adjustment
Valve Adjustment: Hydraulic lifters - check for noise every 30,000 miles
Cooling System: Check radiator, hoses, and water pump for leaks

CAUTION! Engine components operate at high temperatures. Allow engine to cool before servicing.

Transmission & Drivetrain

Transmission Fluid: Check level with engine running, use Dexron II
Shift Linkage: Adjust for proper gear selection
Drive Shaft: Inspect universal joints for wear
Differential: Change fluid every 60,000 miles
Transmission Mounts: Check for deterioration and replace if cracked

Electrical System

Diagnosis and repair of electrical components and wiring.

Battery: Located in trunk, check terminals for corrosion. Alternator: Output 90 amps, test voltage regulation. Starter: Solenoid mounted on starter motor. Fuses: Main fuse box under hood, secondary in glove compartment.

Wiring diagrams available in technical data section. Use multimeter for circuit testing.

Suspension & Steering

Independent suspension with self-leveling system maintenance.

Shock Absorbers: Check for leaks and wear
Ball Joints: Inspect for play during tire rotation
Self-Leveling System: Check hydraulic fluid and pump operation
Steering Gear: Power steering system - check fluid and belt tension
Wheel Alignment: Specifications in technical data section

Tip: Always support vehicle properly with jack stands when working under car.

Brake System

Disc brakes with ABS diagnosis and repair procedures.

Brake Pads: Front and rear pad replacement intervals
Rotors: Measure for minimum thickness specification
Brake Lines: Inspect for corrosion and damage
ABS System: Diagnostic procedures for anti-lock system
Parking Brake: Adjust cable tension for proper operation

WARNING! Brake fluid is hygroscopic - replace every 2 years to maintain braking performance.

Interior & Body

Repair procedures for interior components and body panels.

Seat Mechanisms: Electric seat adjustment troubleshooting. Dashboard: Instrument cluster removal and bulb replacement. Door Panels: Window regulator and lock mechanism repair. Body Panels: Paint codes and rust prevention measures.

Troubleshooting Guide

Symptom	Possible Cause	Corrective Action
Engine won't start	Fuel pump, ignition system	Check fuel pressure, spark, and starter operation
Rough idle	Vacuum leaks, dirty injectors	Inspect vacuum hoses, clean fuel injectors
Transmission slipping	Low fluid, worn bands	Check fluid level and condition, adjust bands
Electrical issues	Bad grounds, alternator	Test battery and charging system, check grounds
Brake vibration	Warped rotors	Resurface or replace brake rotors

Technical Data

Torque specifications, fluid capacities, and special tool requirements.

Engine Oil Capacity: 7.5 quarts with filter
Coolant Capacity: 13.2 quarts
Spark Plug Gap: 0.8 mm (0.031 inches)
Wheel Lug Torque: 90 ft-lbs
Oil Pressure: 14-16 psi at idle, 43-57 psi at 3000 rpm

Safety Precautions

Always disconnect battery before electrical work. Use jack stands when working under vehicle. Wear safety glasses during repairs. Follow proper fluid disposal procedures.

Service: For professional assistance, contact Mercedes-Benz dealership or certified mechanic.