Engine:
4.2L M119 V8 Engine (Mechanical and Electronic Components)
Engine Management:
ME 2.0 Engine Control Unit (ECU) Diagnostics, Sensors, Actuators, Fuel Injection, Ignition System
Transmission:
4-Speed Automatic Transmission (722.5) - Overhaul, Diagnosis, Control Systems
Drivetrain:
Rear-Wheel Drive (RWD), Driveshafts, Differential, Axles
Suspension:
Front and Rear Independent Suspension, Shock Absorbers, Springs, Bushings, Control Arms, Ball Joints
Steering:
Hydraulic Power Steering System, Steering Gear, Linkages
Brakes:
Front and Rear Disc Brakes, ABS (Anti-lock Braking System), Brake Lines, Master Cylinder, Calipers, Rotor Specifications
Electrical System:
12V Electrical System, Battery, Alternator, Starter, Fuses, Relays, Wiring Diagrams
Comfort Systems:
Climate Control (HVAC), Automatic Climate Control System, Doors, Windows, Seats, Sunroof
Body:
Body and Chassis, Exterior Panels, Interior Trim, Door Locks, Bumpers
Lighting:
Headlights, Taillights, Interior Lighting, Bulb Specifications
Fuel System:
Fuel Tank, Fuel Pump, Fuel Filter, Fuel Lines, Fuel Pressure Regulator
Exhaust System:
Exhaust Manifold, Catalytic Converter, Muffler, Pipes
Cooling System:
Radiator, Water Pump, Thermostat, Hoses, Coolant Specifications
Emission Control:
Emission Control Systems, EGR (Exhaust Gas Recirculation), EVAP (Evaporative Emission Control)
Maintenance:
Scheduled Maintenance, Oil Changes, Filter Replacements, Tune-ups, Fluid Checks and Replacements
Diagnostics:
Troubleshooting Charts, Diagnostic Trouble Codes (DTCs), Fault Finding Procedures
Repair:
Component Removal and Installation, Overhaul Procedures, Component Reassembly
Adjustment:
Valve Adjustments (if applicable), Brake Adjustments, Park Brake Adjustment
Specifications:
Torque Specifications, Clearances, Measurements, Diagnostic Specifications
Depth:
Complete Factory Level - From Basic Maintenance to Full Engine and Transmission Rebuilds
Diagnostics Detail:
Detailed Diagnostic Trees, Sensor Data Interpretation, Live Data Analysis (with appropriate tools)
Wiring Diagrams:
Full Electrical Schematics for all Systems
Special Tools:
Identification and Usage of Special Tools Required for Specific Repairs
Configuration:
4.2 Liter (4196 cc) 32-Valve DOHC V8
Bore X Stroke:
89.0 mm x 84.0 mm
Compression Ratio:
10.0:1
Horsepower:
275 hp @ 5700 rpm (SAE Net)
Torque:
295 lb-ft @ 3900 rpm (SAE Net)
Injection Type:
Bosch LH-Jetronic Fuel Injection (Sequential Multi-Port)
Fuel Type:
Premium Unleaded Gasoline (91 Octane or higher recommended)
ECM:
Bosch ME 2.0 (Motor Elektronik 2.0)
Timing System:
Dual Overhead Camshafts (DOHC) with Hydraulic Timing Chain Tensioners and Guides
Oil Capacity:
8.0 Liters (8.5 US Quarts)
Recommended Oil:
SAE 0W-40 or 5W-40 Synthetic Engine Oil meeting MB 229.5 specification
Audio System:
Factory AM/FM Cassette Player with optional CD Changer. Often features premium sound systems.
Navigation:
Optional early generation GPS navigation system, often a primitive map display.
Cruise Control:
Standard electronic cruise control
Parking Sensors:
Optional early rear park assist sensors (Parktronic predecessor).
Telematics:
Early cellular phone integration options might be present depending on original specification.
Climate Control:
Dual-zone automatic climate control with recirculation mode and particle filter.
Seats:
Multi-way power adjustable front seats with memory, heated seats, optional ventilated seats.
Headlights:
Halogen headlights with automatic leveling, Xenon HID headlights were an option on later W140 models but may not be common on 1995 S420.
Oil Change Interval:
Every 10,000 miles or 12 months (whichever comes first), using synthetic oil.
Transmission Service Interval:
Every 40,000 - 60,000 miles (recommended fluid and filter change).
Coolant Flush Interval:
Every 2-3 years or 30,000 miles.
Brake Fluid:
DOT 4 or DOT 4 Plus (MB spec 331.0)
Power Steering Fluid:
MB spec 236.3 Hydraulic Fluid (e.g., Pentosin CHF 11S is often a compatible alternative)
Coolant:
Mercedes-Benz Coolant/Antifreeze (Glycol-based, blue color) - MB spec 325.0
Wiring Harness:
Age-related degradation of insulation, particularly around the engine and transmission harnesses ('biodegradable' wiring).
Headliner:
Sagging headliner fabric due to adhesive failure.
Door Locks:
Vacuum-operated door lock system failures (leaks in vacuum lines or pump).
Cooling System:
Plastic coolant reservoir cracks, water pump seal leaks.
Oil Cooler Seals:
Leaking oil cooler seals leading to coolant contamination.
Transmission Conductor Plate:
Potential failure of the transmission conductor plate in some units, affecting shifting.