Market Segment:
Luxury Sedan/Coupe
Target Audience:
Mercedes-Benz owners, independent repair shops, automotive enthusiasts
Competitors:
BMW 5 Series (E34), Audi V8 Quattro, Lexus LS 400 (from 1989)
Vehicle Selling Points:
Build quality, comfort, safety features, refined driving experience, advanced engineering for its time
Manual Value Proposition:
Enables owners and mechanics to maintain and repair one of Mercedes-Benz's most iconic and durable models, preserving its longevity and performance.
Years Covered:
1988, 1989, 1990, 1991, 1992, 1993
Engine Variants Covered:
All 3.0L Inline-6 (M103) variants
Chassis Variants Covered:
W126 Sedan and Coupe (C126, though primarily focused on Sedan)
Estimated Page Count:
1000+
Type:
Service Repair Workshop Manual
Format:
Digital (likely PDF)
Engine Mechanical:
Complete overhaul, diagnosis, timing, lubrication, cooling system
Engine Electrical:
Ignition system (HFM, EZL), fuel injection (Bosch KE-Jetronic variants), starter, alternator
Transmission Manual:
4-speed Automatic (722.3, 722.4) overhaul, diagnosis, fluid changes
Transmission Automatic:
4-speed Automatic (722.3, 722.4) overhaul, diagnosis, fluid changes
Suspension:
Front and rear suspension, shock absorbers, springs, control arms, bushings
Steering:
Power steering system, steering gearbox, tie rods, linkage
Brakes:
Hydraulic system, ABS (Anti-lock Braking System), brake pads, rotors, calipers, parking brake
Electrical System:
Wiring diagrams, lighting, power windows, power locks, sunroof, central locking, climate control electronics
Body And Frame:
Body panels, doors, hood, trunk, interior trim, chassis diagnostics
Climate Control:
HVAC system, A/C compressor, heater core, blower motor, climate control unit diagnosis
Routine Maintenance:
Oil changes, filter replacements, fluid checks, tune-ups
Engine Repair:
Head gasket replacement, piston and ring replacement, valve stem seals, timing chain/belt replacement (if applicable, though M103 is chain driven)
Transmission Overhaul:
Complete disassembly, inspection, and reassembly of automatic transmissions
Brake System Repair:
Caliper replacement, brake line bleeding, ABS sensor diagnostics
Electrical Troubleshooting:
Diagnosing and repairing wiring faults, component testing
Suspension And Steering Repair:
Ball joint replacement, power steering pump replacement, wheel alignment specifications
Depth:
Comprehensive: From basic maintenance to complete engine and transmission rebuilds, including advanced diagnostics and component-level repair.
Engine Type:
M103.980 (300SE)
Configuration:
3.0L (2962cc) SOHC Inline-6
Bore X Stroke:
88.0 mm x 80.25 mm
Horsepower Net:
189 hp @ 5700 rpm (approx.)
Torque Net:
195 lb-ft @ 4400 rpm (approx.)
Fuel Delivery:
Bosch KE-Jetronic (CIS-E) Fuel Injection
Fuel Type:
Unleaded Premium Unleaded Gasoline (91+ Octane)
Engine Oil Type:
SAE 15W-40 or 10W-30 (API SG or higher)
Engine Oil Capacity:
7.0 Liters (7.4 US Quarts) with filter
Coolant Type:
Mercedes-Benz approved ethylene glycol coolant (e.g., G48)
Coolant Capacity:
10.0 Liters (10.6 US Quarts)
Crash Test Data:
While official NHTSA ratings for this era are limited, the W126 was renowned for its robust safety cage and advanced passive safety features for its time.
ABS:
Standard Anti-lock Braking System (ABS)
Airbags:
Driver's airbag (standard from 1988 onwards)
Seat Belts:
Front seat belt pretensioners
Construction:
Reinforced passenger cell, energy-absorbing crumple zones
Audio System:
Factory premium sound system (e.g., Becker units), often with cassette player
Cruise Control:
Standard electronic cruise control
Phone Integration:
Optional early cellular phone integration (rare)
Climate Control:
Automatic Climate Control (ACC) with cabin air filter
Seats:
Power adjustable front seats with memory, heated seats (optional)
Oil Change Interval:
Every 7,500 - 10,000 miles (or annually)
Transmission Fluid Change:
Every 30,000 - 40,000 miles (recommended)
Coolant Flush:
Every 2-3 years or 30,000 miles
Spark Plug Replacement:
Every 30,000 - 60,000 miles depending on type
Common Wear Items:
Ball joints, tie rod ends, control arm bushings, driveshaft flex discs (guibos), fuel distributor o-rings, idle control valve
Electrical Gremlins:
Wiring harness degradation (especially around engine bay), vacuum leaks affecting idle and performance, headlight switch issues, window regulator failures.
Engine Specific:
Head gasket leaks (less common than later engines, but possible), timing chain tensioner wear (M103 uses a chain, but tensioner can fail), oil cooler leaks.
ABS System:
ABS accumulator failure, wheel speed sensor issues
Manufacturer:
Daimler-Benz AG
Generation:
W126 (Second Generation S-Class)
Production Start Year:
1979
Facelift:
1985 (introduction of 300SE model, updated styling, improved aerodynamics, new engines)
Production Period For 300Se:
1986-1991 (globally), 1988-1993 covered by this manual
Manufacturing Locations:
Germany (Sindelfingen)
Car And Driver Five Best:
The W126 generation (including variants like the 300SE) was a frequent recipient of Car and Driver's 'Ten Best Cars' list during its production run.
Build Quality Perception:
Consistently rated as having exceptional build quality and durability, setting benchmarks for the luxury automotive industry.
Industry Standing:
Considered one of the most reliable and well-engineered luxury sedans of its era.
