Class:
Executive Compact Car / Personal Luxury Coupe
Target Audience:
Discerning buyers seeking quality, durability, comfort, and sophisticated engineering.
Competitors:
BMW 3 Series (E21), Audi 80/Fox, Volvo 240, Peugeot 505, Cadillac Seville (earlier models).
Build Quality:
Renowned for exceptional build quality, longevity, and robust construction.
Comfort And Refinement:
Supple ride quality, quiet cabin, high-quality interior materials, and ergonomic design.
Engineering:
Solid engineering principles, advanced for its time, leading to a durable and reliable vehicle.
Coupe Styling:
Distinctive pillarless coupe design offering a sleek and elegant profile.
Engine:
Complete overhaul, diagnosis, lubrication system, cooling system, fuel injection (Bosch K-Jetronic), ignition system, emission control systems.
Transmission:
Automatic Transmission (e.g., 4-speed 722.1), manual transmission (if applicable for the specific market/build), diagnosis, repair, fluid specifications.
Drivetrain:
Rear-wheel drive system, driveshaft, differential, axle shafts, diagnosis and repair.
Suspension:
Front and rear suspension components, springs, shock absorbers, bushings, alignment procedures, diagnosis.
Brakes:
Hydraulic system, disc brakes (front and rear), brake fluid specifications, replacement, bleeding, parking brake, ABS (if equipped).
Steering:
Power steering system, steering box, tie rods, linkage, diagnosis and repair.
Electrical:
12V electrical system, battery, alternator, starter motor, lighting systems, gauges, switches, wiring diagrams, fuses, relays, troubleshooting.
Body And Chassis:
Body panel removal and installation, rust repair, interior trim, glass replacement, door mechanisms, locks, hinges.
HVAC:
Heating, Ventilation, and Air Conditioning (HVAC) system components, refrigerant, diagnosis and repair.
Maintenance:
Routine oil changes, filter replacements, fluid checks and top-offs, spark plug replacement, belt inspection and adjustment.
Troubleshooting:
Systematic diagnostic procedures for common and uncommon faults, symptom-based troubleshooting guides.
Repair:
Step-by-step instructions for component removal, repair, and reinstallation across all major vehicle systems.
Disassembly Assembly:
Detailed instructions for engine disassembly, transmission overhaul, brake caliper rebuild, etc.
Specifications:
Torque specifications for critical fasteners, component measurements, tolerances.
Depth:
Comprehensive, from basic scheduled maintenance to complete engine and transmission rebuilds, including electrical system diagnostics and body repair.
Engine Type:
Inline-6 Cylinder, DOHC (Double Overhead Camshaft)
Engine Code:
M110.984 (typically)
Displacement:
2.8 Liters (2799 cc)
Horsepower Net SAE:
Approximately 155-160 hp @ 5000-5500 rpm (depending on market and exact configuration)
Torque Net SAE:
Approximately 170-175 lb-ft @ 3500-4000 rpm (depending on market and exact configuration)
Fuel Injection:
Bosch CIS (Continuous Injection System) - K-Jetronic
Fuel Type:
Unleaded gasoline (premium octane recommended)
Ignition Type:
Electronic Ignition with Distributor
Cooling Type:
Liquid-cooled
Oil Capacity:
Approximately 6.5 Liters (6.9 US Quarts) with filter change
Transmission Type:
4-speed Automatic Transmission (722.1 series)
Manual Transmission Availability:
Optional in some markets, typically a 4-speed or 5-speed manual.
Automatic Features:
Hydraulic torque converter, planetary gear sets, controlled by hydraulic pressure and governor.
Automatic Transmission Fluid Type:
Mercedes-Benz Specification 236.1 (e.g., Mobil ATF 220, Dexron II)
Automatic Transmission Fluid Capacity:
Approximately 8-9 Liters (8.5-9.5 US Quarts) for complete fill/overhaul
Wheelbase:
Approximately 2795 mm (110.0 inches)
Length:
Approximately 4725 mm (186.0 inches)
Width:
Approximately 1790 mm (70.5 inches)
Height:
Approximately 1420 mm (55.9 inches)
Curb Weight:
Approximately 1500-1600 kg (3300-3500 lbs), varies with equipment
Gross Vehicle Weight Rating:
Approximately 2050 kg (4520 lbs)
Standard Wheel Size:
14-inch or 15-inch alloy or steel wheels
Standard Tire Size:
175 R14, 185/70 R14, 195/70 R14 (market dependent)
Crash Test Data:
While formal NHTSA/IIHS ratings as known today were not prevalent, the W123 was engineered with significant emphasis on structural integrity and occupant protection for its era, featuring a robust passenger cell and safety crumple zones.
Brakes System:
Four-wheel disc brakes with dual-circuit hydraulic system.
Steering Column:
Collapsible steering column for improved impact protection.
Seat Belts:
Standard front seat belts, optional rear seat belts. Lap and shoulder belts often standard in front.
Interior Design:
Soft-touch dashboard materials, padded surfaces, and recessed controls to minimize injury in a collision.
Audio System:
Factory-installed AM/FM radio with cassette player, often with upgraded speaker options.
Features:
Basic analog controls, optional features like power antenna, multiple speakers.
Cruise Control:
Optional cruise control system, typically vacuum-operated.
Connectivity Features:
N/A (no modern connectivity features like Bluetooth or USB)
Oil Change Interval:
Typically every 7,500-10,000 miles (12,000-15,000 km) or annually, whichever comes first.
Transmission Fluid Interval:
Check every 15,000 miles, change approximately every 30,000-50,000 miles (refer to manual for exact specifications).
Air Filter Replacement:
Every 15,000-20,000 miles or as needed based on driving conditions.
Spark Plug Replacement:
Typically every 20,000-30,000 miles for standard plugs.
Coolant Flush:
Every 2-3 years or 30,000-50,000 miles.
Engine Oil Specification:
API SG/SH or ACEA A2/A3. Viscosity often 10W-40, 15W-40, or 20W-50 depending on climate. Refer to manual for exact recommendations.
Coolant Specification:
Ethylene glycol-based antifreeze, typically a 50/50 mix with distilled water. Mercedes-Benz approved coolant (e.g., Zerex G-05).
Brake Fluid Specification:
DOT 3 or DOT 4 brake fluid.
Power Steering Fluid Specification:
ATF Dexron II or III, or specific Mercedes-Benz specification.
Common Problems:
Rust (wheel arches, door bottoms, sunroof), vacuum system leaks (affecting central locking, cruise control, HVAC), aging rubber components (hoses, bushings), fuel distributor issues (K-Jetronic), transmission shifting issues (especially in older automatics), early climate control failures.
Preventative Measures:
Regular inspection for rust, meticulous maintenance of vacuum lines, timely replacement of rubber components, diligent fluid changes.
Manufacturer Focus:
Mercedes-Benz's commitment to engineering excellence, durability, and premium automobiles.
W123 Lineage:
Successor to the W114/W115 series, it was the first Mercedes-Benz model to be designed from the outset for mass production using computer-aided design (CAD) principles.
Coupe Variant Introduction:
The C123 coupe variant was introduced in 1977, offering a more stylish and personal alternative to the saloon and estate models.
Production Years:
1976-1985 for the W123 platform. The 280C coupe was produced within this range.
Manufacturing Locations:
Primarily Germany, with some assembly in other international locations.
