🏷️ Basic Information

Make:

Mazda

Model:

RX-4

Year:

1978

Body Style:

Coupe, Sedan, Wagon

Chassis Code:

LA2 (Coupe/Sedan), LA3 (Wagon)

Engine Code:

12A (RE2)

👋 Introduction

Target Audience:

Professional automotive technicians and experienced DIY enthusiasts focused on the Mazda RX-4.

Manual Advantage:

Provides specific, factory-approved procedures and specifications, offering a significant advantage over generic repair guides. Essential for correct rotary engine maintenance.

Rotary Focus:

Detailed coverage of the unique aspects of the Mazda Wankel rotary engine, including apex seal maintenance, lubrication systems, and specific diagnostic techniques.

Completeness:

Covers all variants of the RX-4, ensuring all mechanical and electrical systems are addressed for the 1978 model year.

📋 Manual Details

Coverage Scope:

All models, all repairs A-Z

Page Count:

Estimated 700-1000+ pages (typical for comprehensive dealer service manuals of this era)

Manual Type:

Factory Service Manual / Workshop Manual

Language:

English

Format:

Likely printed (original production); digital formats (PDF) commonly available for archival purposes.

📖 Manual Coverage

Engine Management:

Rotary engine (12A) theory of operation, disassembly, assembly, lubrication, cooling, fuel delivery (carburetor), ignition, emissions control systems.

Transmission:

Manual and Automatic transmissions, clutch, driveline, differentials.

Chassis:

Suspension systems (front and rear), steering system, brake system (including hydraulic circuits and components), wheel bearings.

Electrical:

Wiring diagrams for all circuits, charging system (alternator), starting system (starter motor), lighting, instrumentation, ignition system, horns, wipers, radios, power windows/locks (if equipped).

Body And Trim:

Body panel removal and installation, glass, trim pieces, interior components, door mechanisms, seat adjustments, convertible top mechanisms (if applicable).

Maintenance:

Routine maintenance checks, oil changes, filter replacements, spark plug (rotor seal inspection/replacement) intervals, fluid checks and top-ups, drive belt adjustments.

Diagnostics:

Troubleshooting charts and procedures for common and uncommon issues, diagnostic trouble codes (if applicable for the era), fuel system diagnostics, ignition system diagnostics, electrical system testing.

Repair:

Step-by-step repair procedures for major components and systems, including engine rebuilds, transmission overhauls, brake caliper replacement, suspension component replacement.

Specification Data:

Torque specifications, clearance specifications, alignment specifications, electrical resistance values, vacuum hose routing diagrams.

Depth Of Information:

Comprehensive; covers everything from basic fluid changes to full engine and transmission rebuilds, including detailed internal component procedures and specifications.

📊 Manual Specifications

Digital Quality:

High-resolution scans with clear text and images; searchable text if digitally formatted.

Print Standard:

Professional printing with clear diagrams, schematics, and text; durable paper stock typical for workshop manuals.

Binding Style:

Original likely hardcover or heavy-duty softcover with saddle-stitch or perfect binding for durability in a workshop environment.

Paper Quality:

Durable, often coated paper to resist grease and shop fluids, designed for longevity.

⚙️ Engine Specifications

Engine Type:

Wankel Rotary

Engine Code:

12A (RE2)

Rotor Design:

Two-rotor

Displacement:

1.146 L (equivalent to approx. 2.3 L piston displacement for tax purposes)

Horsepower:

Approximately 100-110 hp (SAE Gross) depending on emissions equipment and tuning.

Torque:

Approximately 100-115 lb-ft (SAE Gross) depending on tuning.

Fuel Delivery:

Single or Twin Barrel Downdraft Carburetor (e.g., Hitachi or Mikuni)

Fuel Type:

Unleaded Regular Octane (as mandated for 1978 models)

Cooling Type:

Water-cooled

Oil Type Recommendation:

API SF or SG rated SAE 10W-30 or 10W-40 (specific Mazda recommendations will be in the manual)

Oil Capacity:

Approximately 5.2 US quarts (4.9 liters) with filter change (verify with manual).

🔧 Transmission

Transmission Type Standard:

4-speed Manual Transmission

Transmission Type Optional:

3-speed Automatic Transmission

Clutch Type:

Single Dry Plate, Diaphragm Spring

Manual Gear Ratios:

Specific gear ratios for 4-speed manual will be detailed in the manual.

Automatic Gear Ratios:

Specific gear ratios for 3-speed automatic will be detailed in the manual.

Transmission Fluid Type:

Dexron II (or equivalent) for Automatic; GL-4 rated gear oil for Manual (verify with manual).

📐 Dimensions

Wheelbase:

Approximately 98.0 inches (2489 mm)

Overall Length:

Approximately 170.0 inches (4318 mm)

Overall Width:

Approximately 65.0 inches (1651 mm)

Overall Height:

Approximately 50.8 inches (1290 mm) for Coupe, slightly higher for Sedan/Wagon.

Curb Weight:

Approximately 2300-2500 lbs (1043-1134 kg) depending on body style and equipment.

Gross Vehicle Weight Rating:

Will be specified in manual for load limits.

Wheel Bolt Pattern:

4 x 110mm

Standard Tire Size:

175/70SR13 or similar (verify with manual).

Standard Wheel Size:

13 x 5J

🛡️ Safety Features

Crash Safety Era:

Standards for 1978 were significantly different from modern standards. Manual will not contain NHTSA/Euro NCAP ratings.

Braking System:

Front Disc Brakes, Rear Drum Brakes.

Steering System:

Recirculating Ball Steering (Power steering often optional).

Seatbelts:

Standard lap and shoulder belts (3-point).

Body Structure:

Reinforced chassis and body for the era.

💡 Technology Features

Audio System:

Factory AM/FM radio, often with an optional 8-track player or cassette deck.

Instrumentation:

Analog gauges including speedometer, tachometer, fuel level, coolant temperature, oil pressure, and voltage.

Driver Aids:

Basic for the era: conventional braking system, no ABS or traction control.

Connectivity Features:

N/A (No modern connectivity features).

🔧 Maintenance

Oil Change Interval:

Typically every 3,000-5,000 miles (5,000-8,000 km) or 3-6 months (refer to manual for precise interval).

Air Filter Replacement:

Every 15,000-30,000 miles (24,000-48,000 km) or as needed based on driving conditions.

Spark Plug Maintenance:

Rotary engines have specific apex seal wear patterns. Apex seal inspection/replacement typically at higher mileage intervals. Plug changes are less frequent than piston engines.

Coolant Flush:

Every 2 years or 30,000 miles (48,000 km).

Coolant Type:

Ethylene Glycol based antifreeze (50/50 mix with distilled water).

Brake Fluid Type:

DOT 3 or DOT 4.

Power Steering Fluid:

ATF Dexron II (if equipped with power steering).

Apex Seal Wear:

The most critical wear item in a Wankel engine. Symptoms include loss of compression, hard starting, increased oil consumption, and reduced power. Regular oil changes and proper warm-up/cool-down are crucial.

Carburetor Issues:

Varnish build-up, vacuum leaks, and worn throttle shafts can affect drivability and fuel economy. Regular cleaning and adjustment are beneficial.

Ignition System:

Points and condenser wear in the distributor, coil failure, and distributor cap/rotor issues can lead to misfires.

Oil Metering System:

The system that injects oil into the engine for apex seal lubrication can fail, leading to premature seal wear. Ensure it is functioning correctly.

📚 Vehicle History

Mazda Rotary Pioneering:

Mazda's commitment to the Wankel rotary engine, starting with the Cosmo, continued with the R100, RX-2, RX-3, and culminating in the RX-4 and later RX-7.

Rx 4 Positioning:

The RX-4 (codenamed LA) was introduced in 1972 in Japan as the 'Rotor' and was sold internationally from 1973. It represented a more refined and larger platform than the RX-3, offering coupe, sedan, and wagon variants. The 1978 model is part of the later series with minor styling updates.

Production Years:

1972-1977 (Japan), 1973-1978 (International)

Manufacturing Location:

Japan