RX-4 (Luce)

1972-1977 / Coupe / Sedan / Japan

All RX-4 (Luce) problems All workshop issues

Minor Cooling System

Radiator Inadequacy

Symptoms

The engine runs hot, particularly in traffic or on hot days. The temperature gauge creeps up or the engine overheats.

Cause

The factory radiator is 50+ years old and was designed for 1970s traffic conditions. Reduced coolant flow through corroded core tubes, blocked fins, and degraded end tanks all reduce cooling capacity. The rotary engine produces significant heat relative to its displacement.

Fix

Replace with an aftermarket aluminium radiator.

Multiple options available for the RX-3 from rotary specialists.

Cost: $300-600 for a quality alloy radiator.

This is one of the best value upgrades you can make.

Cost mentioned in fix

Cost: $300-600 for a

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Other known issues

Minor Cooling System

Thermostat and Water Pump

Overcooling (thermostat stuck open, engine never reaches proper operating temperature) or overheating (thermostat stuck closed, water pump failure).

Minor Engine, Rotary-Specific Issues

Apex Seal Wear and Failure

Gradual loss of compression, reduced power output, difficulty starting (especially when hot), increased oil consumption, and eventually the engine won't sustain combustion. In catastrophic failure, a broken apex seal fragment can score the rotor housing surface, requiring housing replacement.

Minor Engine, Rotary-Specific Issues

Rotor Housing Scoring

Deep scratches or grooves in the chrome or Nikasil coating of the rotor housing inner surface. Reduces compression even with new apex seals. Visible during engine disassembly.

Common Engine, Rotary-Specific Issues

Oil Metering Pump Failure

The engine receives insufficient oil for apex seal lubrication. The apex seals run dry, wear accelerates dramatically, and catastrophic engine failure follows. There may be no warning, the engine simply starts losing compression faster than normal.

Critical Engine, Rotary-Specific Issues

Coolant Seal (O-ring) Failure

Coolant leaks into the combustion chamber (white smoke from exhaust, coolant loss without external leak) or coolant leaks externally from the engine block mating surfaces. The engine overheats.

Minor Engine, Rotary-Specific Issues

Carbon Buildup

Hard carbon deposits accumulate on the rotor faces, apex seal grooves, and exhaust ports. The deposits restrict apex seal movement in their grooves, causing the seals to stick and lose their spring tension against the housing. Compression drops, power decreases, and the engine runs rough.

View all 15 RX-4 (Luce) problems