Engine Mechanical:
Engine assembly, cylinder head, valve train, crankshaft, pistons, connecting rods, lubrication system, cooling system, intake and exhaust systems
Engine Management:
Fuel injection (Bosch KE-Jetronic/LH-Jetronic), ignition system, electronic control unit (ECU), sensors, actuators, emissions control
Transmission:
4-speed Automatic Transmission (722.3xx series), gear ratios, hydraulic control, torque converter, shift logic, service and repair
Drivetrain:
Driveshafts, CV joints, differential, rear axle assembly
Suspension:
Front McPherson struts, rear multi-link independent suspension, springs, shock absorbers, bushings, alignment specifications
Steering:
Hydraulic power steering system, steering gearbox, tie rods, steering column, service and troubleshooting
Brakes:
Front ventilated discs, rear solid discs, hydraulic system, ABS (Anti-lock Braking System), brake pad and rotor replacement, bleeding procedures
Electrical System:
12V electrical system, battery, alternator, starter motor, lighting circuits, fuses, relays, wiring diagrams
Body And Chassis:
Body construction, doors, hood, trunk, bumpers, glass, interior trim, chassis components
Climate Control:
HVAC system, air conditioning (R134a), heating system, blower motor, control panel, refrigerant service
Interior:
Seats, dashboard, instrumentation, door panels, headliner, seat belts
Safety Systems:
Airbags (if equipped), seatbelt pretensioners
Maintenance:
Scheduled maintenance intervals, oil changes, fluid checks and changes, filter replacements, spark plug replacement, belt inspection/replacement
Troubleshooting:
Diagnostic procedures, fault code interpretation, common problem diagnosis for engine, transmission, electrical, and other systems
Repair:
Step-by-step repair instructions for all major components and systems, including engine overhauls, transmission rebuilds, brake system repairs, suspension component replacement
Diagnostics:
Detailed diagnostic flowcharts, resistance values, voltage readings, signal checks for sensors and actuators
Wiring Diagrams:
Complete electrical schematic diagrams for all vehicle systems, including engine control, lighting, power accessories, ABS, etc.
Specifications:
Torque specifications for all fasteners, engine clearances, fluid capacities, alignment data, pressure specifications
Depth:
Expert Level - Covers all aspects from basic maintenance to complete engine and transmission rebuilds, complex electrical diagnostics, and bodywork.
Oil Change Interval:
Every 7,500 - 10,000 miles (12,000 - 16,000 km) or 1 year, whichever comes first (using synthetic oil)
Transmission Fluid Change:
Every 30,000 - 60,000 miles (50,000 - 100,000 km) (recommended, dependent on driving conditions)
Coolant Change:
Every 2-3 years or 30,000 - 50,000 miles
Spark Plug Replacement:
Refer to manual, typically around 60,000-100,000 miles depending on type (e.g., iridium)
Engine Oil:
API SJ/SL or higher, SAE 5W-40 or 10W-40 (synthetic recommended)
Coolant:
MB-Approval 325.0 or 326.0 (Glycol-based, Ethylene Glycol)
Common Problems Engine:
Head gasket leaks (less common on M104 than early M103), oil leaks from valve cover gaskets and oil cooler seals, distributor rotor issues, timing chain tensioner wear
Common Problems Electrical:
Wiring harness degradation (cracking insulation), blower motor resistor failure, ABS sensor failures, central locking issues
Common Problems Chassis:
Sagging suspension (worn front sway bar links/bushings, rear self-leveling suspension issues if equipped), fuel pump relay failure, vacuum leaks
Common Problems Body:
Sunroof drain blockage, window regulator issues, door seal degradation
