Systems Covered:
Engine, Transmission, Drivetrain, Suspension, Steering, Brakes, Electrical System, Body, Interior, HVAC, Fuel System, Cooling System, Exhaust System, Emission Control, Diagnostics, Troubleshooting, Maintenance, Repair Procedures, Wiring Diagrams, Specifications.
Page Count:
Extensive (typically 1000+ pages for a full factory service manual).
Manual Type:
Factory Authorized Service Repair Workshop Manual
Format:
Digital (PDF) or Printed
Engine Mechanical:
Detailed disassembly, inspection, repair, and reassembly of all engine components, including cylinder head, block, pistons, rings, crankshaft, camshafts, valvetrain, timing components, seals, and gaskets. Covers all gasoline engine variants for 1991 model year.
Engine Management And Fuel:
In-depth coverage of fuel injection systems (Bosch KE-Jetronic or similar), ignition system, electronic control unit (ECU) operation, sensors, actuators, emission control systems (catalytic converter, EGR), fuel pump, fuel filter, fuel tank, and lines. Includes diagnostic procedures and troubleshooting for fuel delivery and ignition timing.
Transmission:
Comprehensive repair and service information for both manual and automatic transmissions. Covers clutch operation, gearbox disassembly/reassembly, torque converter, valve body, internal components, fluid changes, and troubleshooting for all applicable transmission types.
Drivetrain:
Details on rear-wheel drive system, including driveshaft, universal joints, differential, axles, and wheel bearings. Includes inspection, lubrication, and repair procedures.
Suspension And Steering:
Complete service and repair for front and rear suspension systems (e.g., MacPherson struts, independent rear suspension), shock absorbers, springs, control arms, ball joints, bushings, and steering system (power steering pump, steering gear/rack and pinion, tie rods). Includes alignment specifications and procedures.
Brakes:
Thorough coverage of hydraulic brake system, including brake discs, calipers, pads, master cylinder, brake lines, ABS (if equipped), parking brake, and brake fluid specifications. Includes bleeding procedures and troubleshooting.
Electrical System:
Detailed wiring diagrams for all electrical circuits, including lighting, starting and charging system (alternator, starter), battery, fuses, relays, switches, instruments, power accessories, and engine management wiring. Includes troubleshooting guides for common electrical faults.
Body And Interior:
Information on body panel removal and installation, door mechanisms, latches, hinges, glass replacement, interior trim, seat adjustments, dashboard components, and body repair techniques. May include convertible top mechanisms if applicable to specific trims.
Heating Ventilation And Air Conditioning HVAC:
Service and repair of the HVAC system, including refrigerant charging (R12 for this era), compressor, condenser, evaporator, blower motor, climate controls, and ductwork. Includes troubleshooting for cooling and heating performance.
Routine Maintenance:
Detailed instructions for oil changes, filter replacements (oil, air, fuel), spark plug replacement, coolant flushes, brake fluid changes, power steering fluid changes, and general inspection points. Includes recommended service intervals.
Troubleshooting:
Systematic diagnostic procedures and flowcharts for identifying and resolving common mechanical, electrical, and performance issues. Covers symptoms, potential causes, and repair steps.
Major Repairs:
Step-by-step instructions for major component overhauls and replacements, such as engine rebuilds, transmission overhauls, cylinder head replacement, suspension component replacement, and brake system repairs.
Diagnostics:
Information on diagnostic trouble codes (DTCs) if applicable to the ECU, sensor testing, actuator testing, and methods for using diagnostic tools (though on-board diagnostics were less sophisticated than modern vehicles).
Wiring Diagrams:
Comprehensive, clearly illustrated wiring diagrams for all vehicle systems, enabling technicians to trace circuits and diagnose electrical faults accurately.
Depth:
Comprehensive, covering everything from basic preventative maintenance to complete engine and transmission rebuilds. Includes detailed torque specifications, tolerances, and procedural steps essential for professional repair.
Engine Variant 1991:
2.3L Inline-4 (M102.962 or similar)
Displacement 2 3L:
2299 cc
Horsepower 2 3L Est:
130-135 hp @ 5100 rpm (approximate, depending on specific engine code and market)
Torque 2 3L Est:
145-150 lb-ft @ 3000-3500 rpm (approximate)
Engine Variant 2 6L:
2.6L Inline-6 (M103.940 or similar)
Displacement 2 6L:
2597 cc
Horsepower 2 6L Est:
160-165 hp @ 5800 rpm (approximate)
Torque 2 6L Est:
177 lb-ft @ 3500 rpm (approximate)
Fuel Injection Type:
Bosch KE-Jetronic Mechanical Fuel Injection (K-Jetronic with electronic control for Lambda/mixture control)
Fuel Type:
Unleaded Gasoline (Octane Rating: 91 RON minimum recommended)
0 60 Mph Est 2 3L:
9.0 - 10.5 seconds (approximate, depending on transmission and condition)
0 60 Mph Est 2 6L:
8.0 - 9.0 seconds (approximate)
Crash Test History:
The W201 platform was recognized for its safety innovations, including a reinforced safety cage and energy-absorbing crumple zones. While official NHTSA ratings for this specific year might not be directly comparable to modern standards, it was considered a very safe vehicle for its era.
ABS Availability:
Optional, depending on trim and market. Anti-lock Braking System (ABS) was available on many models.
Traction Control Availability:
Rare, not commonly found on standard 1991 models. More prevalent on later or performance variants.
Airbags:
Driver's side airbag was optional and becoming more common by 1991. Passenger airbag was not typically offered on this model year.
Seatbelts:
Front seatbelt pretensioners were often standard or optional.
Structural Safety:
Reinforced cabin structure, energy-absorbing steering column, and impact-tested dashboard.
Oil Change Interval:
Typically every 10,000-15,000 km (6,000-9,000 miles) or 12 months, whichever comes first. Consult manual for exact recommendation.
Air Filter Replacement:
Every 20,000-30,000 km (12,000-18,000 miles) or as needed based on driving conditions.
Fuel Filter Replacement:
Typically every 30,000-40,000 km (18,000-25,000 miles).
Spark Plug Replacement:
Every 40,000-60,000 km (25,000-37,000 miles), depending on spark plug type (e.g., standard, multi-electrode).
Engine Oil Type:
API SG or higher, SAE 15W-40 or 10W-40 (check manual for climate suitability and exact MB Spec, e.g., MB 229.1).
Engine Oil Capacity:
Approx. 5.5-6.5 liters (5.8-6.9 US quarts) with filter change (for 2.3L).
Coolant Type:
Ethylene Glycol based antifreeze, typically a 50/50 mix with distilled water. MB Spec 325.0 or equivalent.
Brake Fluid Type:
DOT 3 or DOT 4 (refer to manual for specific DOT rating and MB Spec).
Common Wear Items:
Vacuum hose degradation, front suspension bushings and ball joints, rear subframe bushings, fuel pump relay failure, mass airflow sensor (if equipped), alternator brushes, window regulator mechanisms, and early ABS sensor issues.
Engine Specific Notes:
M102 engines can develop oil leaks from front timing cover and rear main seal. M103 engines (2.6L) are generally robust but can have head gasket issues if overheated.
Electrical Common Failures:
Fuse box contacts, door lock actuators, and dashboard instrument cluster illumination can fail over time.