🏷️ Basic Information

Make:

Mercedes-Benz

Model:

W123 280C

Body Style:

Coupe

Chassis Code:

W123.043

Generation Code:

W123

Engine Code:

M110 (likely, for 2.8L variant)

👋 Introduction

Segment:

Luxury Executive Coupe.

Target Audience:

Owners seeking detailed technical guidance for DIY maintenance and repair of their W123 280C, as well as professional mechanics.

Key Competitors:

BMW E12 6 Series, Audi 80/90 Coupe, Jaguar XJ-S, Volvo P1800/P1800ES (earlier), various American luxury coupes of the era.

Reliability Focus:

Emphasizes adherence to service schedules and proper repair procedures for long-term reliability and performance.

Diy Empowerment:

Designed to empower owners and technicians with the knowledge to perform complex tasks, fostering self-sufficiency.

Technical Accuracy:

Commitment to providing factory-correct information, procedures, and specifications.

Comprehensive Scope:

Covers virtually all aspects of the vehicle's mechanical and electrical systems.

📋 Manual Details

Covered Years:

1976, 1977, 1978, 1979, 1980, 1981, 1982, 1983, 1984, 1985

Total Pages:

559

Type:

Workshop Service Repair Manual

Language:

English

Format:

PDF

📖 Manual Coverage

Engine:

Complete engine overhaul, diagnosis, testing, adjustments, removal/installation of major components (cylinder head, block, crankshaft, camshafts, lubrication system, cooling system, fuel system, ignition system).

Transmission:

Diagnosis, adjustment, removal/installation of automatic and manual transmissions, shift linkage, torque converter (for automatic).

Drivetrain:

Rear axle, driveshaft, CV joints, differential (diagnosis, overhaul, fluid service).

Suspension:

Front and rear suspension components (control arms, ball joints, bushings, springs, shock absorbers), alignment procedures, diagnosis of wear.

Steering:

Power steering system (pump, hoses, gearbox), steering linkage, diagnosis and repair.

Brakes:

Front and rear disc brakes, calipers, pads, rotors, master cylinder, brake lines, parking brake system, diagnosis and bleeding procedures.

Electrical System:

Battery, charging system (alternator, regulator), starting system (starter), ignition system (distributor, coil, plugs, wires), lighting system, gauges, dashboard instruments, fuse box, wiring diagrams.

Fuel System:

Fuel pump, fuel filter, fuel lines, fuel injection system (likely Bosch K-Jetronic for 280C), carburetor (if applicable to specific sub-models), fuel tank, emissions control system.

Cooling System:

Radiator, thermostat, water pump, fan, hoses, coolant, diagnosis and repair.

Exhaust System:

Exhaust manifolds, pipes, catalytic converter (depending on market and year), mufflers, hangers, diagnosis and repair.

Body And Interior:

Body panels, doors, windows, locks, seals, trim, seats, dashboard, climate control system (HVAC), headliner, carpeting, glass replacement.

Chassis And Frame:

Frame inspection, body mounting, structural components.

Maintenance:

Scheduled maintenance, oil changes, filter replacements, fluid checks and top-offs, lubrication, belt tensioning, spark plug replacement, tune-ups.

Troubleshooting:

Systematic diagnosis of common and uncommon problems, symptom-based troubleshooting guides, fault code interpretation (if applicable).

Repair:

Step-by-step instructions for component repair, disassembly and reassembly of all major systems, component replacement.

Installation:

Proper procedures for installing new or replacement parts and components.

Adjustment:

Precise adjustments for engine timing, idle speed, carburetor/fuel injection settings, brake adjustments, suspension alignment.

Diagnosis:

Detailed diagnostic procedures for electrical, mechanical, and fuel systems.

Depth:

Comprehensive, covering basic maintenance to complete engine and transmission rebuilds, including detailed diagnostics and specifications.

Special Tools:

References to and illustrations of required special service tools (SSTs) and factory-specific equipment.

Specifications:

Inclusion of critical technical data, including torque specifications, wear limits, clearances, fluid capacities, and electrical values.

Pictorial Guidance:

Detailed illustrations, exploded diagrams, drawings, and photographs to guide users through procedures.

📊 Manual Specifications

Format:

PDF

Searchability:

Likely searchable text content within the PDF.

Printability:

Yes, all pages are printable.

Resolution:

Assumed high-resolution suitable for printing.

Binding:

N/A (Digital PDF)

Paper:

N/A (Digital PDF)

Os Compatibility:

Windows, Mac, Linux OS.

Software Requirement:

Adobe Reader.

⚙️ Engine Specifications

Engine Type:

Inline 6-cylinder, naturally aspirated (M110 engine family).

Displacement:

2.8 Liters (2787 cc).

Bore X Stroke:

86.0 mm x 80.25 mm (approximate, for M110).

Compression Ratio:

Typically around 8.0:1 or 8.7:1 depending on variant/market.

Valve Train:

Dual Overhead Camshafts (DOHC), 2 valves per cylinder.

Horsepower:

Approximately 142-158 hp (SAE Gross) or 130-145 hp (SAE Net), depending on fuel injection and emissions equipment.

Torque:

Approximately 160-175 lb-ft (SAE Gross) or 145-160 lb-ft (SAE Net), depending on fuel injection and emissions equipment.

Fuel Delivery:

Likely Bosch K-Jetronic mechanical fuel injection system for most W123 280 models, potentially Carburetor on earlier or specific market versions, though less common for the 280C in this timeframe.

Fuel Type:

Unleaded gasoline (premium recommended).

Engine Oil Type:

Refer to manual for specific viscosity (e.g., SAE 10W-40, 15W-40, or 20W-50 depending on climate and service recommendations).

Engine Oil Capacity:

Approximately 6.5-7.0 liters (6.9-7.4 US quarts) with filter change. Specific capacity should be verified in the manual.

Coolant Type:

Ethylene glycol based antifreeze/coolant, typically a 50/50 mix with distilled water.

🔧 Transmission

Type:

4-speed automatic transmission (e.g., 722.1 or 722.3 series) was common. Manual transmissions (e.g., 4-speed or 5-speed) were also available.

Type:

4-speed or 5-speed manual transmission.

Automatic Features:

Torque converter, hydraulic control, potentially a torque converter lock-up clutch on later models for improved fuel economy.

Automatic Transmission Fluid:

MB Specification 236.3 (e.g., Dexron II or equivalent is often compatible but MB spec is preferred).

Manual Transmission Fluid:

Refer to manual; typically a gear oil with specific viscosity (e.g., GL-4 75W-90 or 80W-90).

Automatic Transmission Capacity:

Approximately 2.5 liters (2.6 US quarts) for torque converter refill, total capacity around 8-9 liters. Exact figure from manual is critical.

📐 Dimensions

Length:

Approximately 4725 mm (186.0 in) for coupe.

Width:

Approximately 1790 mm (70.5 in).

Height:

Approximately 1425 mm (56.1 in) for coupe.

Wheelbase:

Approximately 2795 mm (110.0 in).

Curb Weight:

Approximately 1500-1600 kg (3300-3520 lbs), depending on equipment.

Gross Vehicle Weight Rating:

Refer to vehicle's compliance plate or manual.

Standard Tire Size:

Commonly 195/70R14 or 205/70R14.

Wheel Bolt Pattern:

5x112 mm.

Wheel Offset:

ET20 to ET25 (typical for Mercedes-Benz of this era).

🛡️ Safety Features

Crash Test Data:

While specific NHTSA/Euro NCAP ratings for this era are scarce, the W123 chassis was engineered with a strong focus on structural integrity, crumple zones, and occupant protection for its time.

Braking System:

Four-wheel disc brakes (front ventilated) with dual-circuit hydraulic system.

Steering System:

Recirculating ball steering with power assistance (standard on most 280C).

Body Construction:

Reinforced passenger cell, energy-absorbing front and rear sections.

Seat Belts:

Standard front seat belts, often with inertia reels. Rear seat belts usually lap belts, with some later models potentially having three-point belts.

Steering Column:

Collapsible steering column.

Windshield:

Laminated safety glass.

💡 Technology Features

Audio System:

Factory-installed radio with AM/FM, often with manual tuning. Cassette players became more common during the production run. Speakers were typically limited in number and placement compared to modern vehicles.

Controls:

Basic dashboard layout with physical knobs and switches for climate control, lighting, and audio.

Cruise Control:

Optional on many models.

Climate Control:

Manual or optional automatic climate control (Thermatic/Thermotronic) systems, utilizing vacuum-actuated flaps and a blower motor.

Connectivity Features:

None in the modern sense. Antennas for radio reception were the primary external connection.

🔧 Maintenance

Oil Change Interval:

Typically every 5,000-7,500 miles (8,000-12,000 km) or annually. Specific interval depends on driving conditions and oil type used. Consult manual.

Major Service:

Refer to periodic maintenance chart in manual. Major services often involve checking/replacing spark plugs, fuel filter, air filter, ignition points (if applicable), valve adjustments, and comprehensive inspection.

Transmission Service:

Automatic transmission fluid and filter change recommended every 30,000-50,000 miles (50,000-80,000 km). Manual transmission fluid service intervals vary; consult manual.

Power Steering Fluid:

Refer to manual; typically a hydraulic fluid compatible with Mercedes-Benz specifications. Avoid generic ATF unless specified.

Brake Fluid Type:

DOT 3 or DOT 4 hydraulic brake fluid.

Coolant Capacity:

Approximately 8-10 liters (8.5-10.6 US quarts), depending on engine and radiator size. Consult manual.

Common Problems:

Rust (especially around wheel arches, door bottoms, sunroof, and jacking points), vacuum system leaks affecting central locking and climate control, aging rubber components (bushings, hoses), potential K-Jetronic fuel distributor issues, wiring harness degradation over time, starter solenoid issues.

Maintenance Recommendations:

Regular inspection for rust, proactive replacement of vacuum hoses and rubber components, consistent fluid changes, checking fuel delivery system components, and ensuring all electrical connections are clean and secure.

📚 Vehicle History

Mercedes Benz Legacy:

Mercedes-Benz has a long-standing reputation for engineering excellence, durability, and safety, established over decades prior to the W123.

W123 Lineage:

The W123 series (produced 1976-1985) succeeded the W114/W115 series and was known for its exceptional build quality, comfort, and mechanical robustness. It was available in sedan, wagon, coupe, and long-wheelbase versions.

280C Positioning:

The 280C represented the higher-end, more powerful coupe variant within the W123 lineup, offering enhanced performance and a more luxurious aesthetic.

Production Period:

1976-1985.

Manufacturing Locations:

Primary production in Stuttgart, Germany, with assembly plants in various countries.

🏆 Awards & Recognition

Industry Perception:

The W123 series is widely regarded as one of the most durable and over-engineered Mercedes-Benz models ever produced, earning a reputation for longevity and reliability in various global markets. It's often cited in 'most reliable car' lists for its era.

Long Term Durability:

Consistently praised for its robust engineering, leading to high survival rates and longevity.

Manual Quality:

Marketed as '100% COMPLETE and INTACT', indicating a high standard of documentation and no missing sections.