Engine Mechanical:
Engine assembly, disassembly, cylinder head, block, crankshaft, pistons, connecting rods, valve train, timing, lubrication, cooling.
Engine Fuel System:
Fuel injection (Bosch K-Jetronic, KE-Jetronic), carburetors (where applicable), fuel pump, lines, filters, components.
Engine Ignition System:
Distributor, ignition coil, spark plugs, wiring, timing adjustments.
Transmission:
Manual transmission (4-speed, 5-speed), automatic transmission (3-speed, 4-speed), clutch, driveshafts, differentials.
Suspension And Steering:
Front suspension (independent, McPherson struts), rear suspension (independent, semi-trailing arms), shock absorbers, springs, ball joints, bushings, steering box, power steering.
Brakes:
Front disc brakes, rear drum brakes (later models may have rear discs), brake system components, hydraulic lines, master cylinder, calipers, wheel cylinders, parking brake.
Electrical System:
Battery, alternator, starter motor, lighting system, wipers, horn, dashboard instruments, fuse box, wiring diagrams, relays.
HVAC System:
Heating, ventilation, and air conditioning (if equipped), components, diagnosis, and repair.
Body And Chassis:
Body panels, doors, hood, trunk, glass, interior trim, structural components, corrosion prevention.
Body Electrical:
Power windows, central locking, power mirrors, radio systems, speaker installation.
Routine Maintenance:
Oil changes, filter replacements, fluid checks and top-ups, spark plug replacement, belt inspections and adjustments.
Troubleshooting:
Diagnostic procedures for common faults and symptoms across all major systems.
Repair And Rebuild:
Step-by-step instructions for component removal, repair, and reinstallation for engine, transmission, suspension, brakes, etc.
Disassembly And Assembly:
Detailed instructions for taking apart and putting back together various vehicle components and sub-assemblies.
Cleaning And Installation:
Procedures for cleaning parts during overhaul and correct installation techniques.
Technical Specifications:
Torque values, clearances, timing settings, fluid capacities, electrical specifications.
Wiring Diagrams:
Comprehensive electrical schematics for all vehicle systems.
Depth Of Coverage:
Comprehensive (suitable for professional technicians and advanced DIYers), covering most mechanical and electrical repairs.
Engine Variants Covered:
Wide range of 4-cylinder and 6-cylinder gasoline (e.g., M115, M110) and diesel (e.g., OM615, OM616, OM617) engines offered during the W123 production run.
Typical Power Output Gasoline:
Ranges from approx. 75 hp (200) to 185 hp (300E).
Typical Power Output Diesel:
Ranges from approx. 72 hp (200D) to 88 hp (300D, 300TD).
Fuel Delivery Gasoline:
Primarily Bosch K-Jetronic (CIS) continuous injection, some early models might have carburetors. Later models (post-1981/82) could feature KE-Jetronic (CIS-E).
Fuel Delivery Diesel:
Bosch inline mechanical fuel injection pump.
Oil Capacity Example:
Typically 6-8 liters (approx. 6.3-8.5 US quarts) depending on engine variant and oil filter.
Coolant Type:
Typically a 50/50 mix of approved antifreeze and distilled water. Consult manual for specific MB approval numbers.
Standard Transmission Offered:
Often a 4-speed manual transmission was standard on lower-tier models.
Optional Transmission Offered:
3-speed and later 4-speed automatic transmissions were widely available and popular options.
Automatic Transmission Control:
Hydraulic control, often with vacuum modulator for engine load compensation.
Automatic Transmission Fluid Type:
Typically MB-specific ATF (e.g., Dexron II or equivalent, consult manual for exact MB spec).
Manual Transmission Fluid Type:
GL-4 or GL-5 gear oil, specific viscosity grade (e.g., 75W-90, 80W-90) depends on transmission type and climate. Consult manual.
Oil Change Interval:
Typically every 10,000 - 15,000 km (6,000 - 9,000 miles) or annually, depending on driving conditions and oil used. Consult manual for exact recommendation.
Transmission Fluid Change:
Automatic: Typically 40,000 - 60,000 km (25,000 - 37,000 miles). Manual: Less frequent, often checked during clutch service. Consult manual.
Coolant Change:
Typically every 2-3 years or 40,000-60,000 km (25,000-37,000 miles).
Engine Oil Specification Example:
API SG or higher, SAE 10W-40 or 15W-40 recommended for most conditions. Diesel engines might have specific oil requirements (e.g., API CD). Always check manual for exact MB approval.
Brake Fluid Specification:
DOT 3 or DOT 4, depending on system design. Consult manual for precise specification.
Common Wear Items:
Rubber bushings (suspension, exhaust mounts), vacuum lines (climate control, engine management), fuel accumulators (CIS), and some electronic components in later models.
Diesel Specific Issues:
Glow plug system reliability, vacuum leak issues affecting starting and idle.
Body Corrosion:
Susceptible to rust, particularly in wheel arches, sills, and around window seals, especially in regions with heavy road salt use.
