RX-7 (FC)

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.

The apex seals are the equivalent of piston rings, they maintain the gas-tight seal between the rotor faces and the epitrochoid-shaped housing. Every rotation, the apex seals sweep across the housing surface under spring tension and combustion pressure. Over tens of thousands of rotations, the seal material wears down. The rate of wear depends on lubrication (oil metering pump function and pre-mixing), operating temperature, combustion temperature, and carbon deposit buildup.

Full engine strip and rebuild. The engine is removed, disassembled, and all seals (apex seals, side seals, corner seals, oil seals) are replaced. The rotor housings are inspected and resurfaced or replaced if scored. The rotors themselves are inspected for wear. A quality rebuild costs $2,500-4,000 for the 12A and includes all seals, bearings, and gaskets. The 10A is slightly less due to smaller components but parts are scarcer.

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.

Foreign material passing through the engine (debris from a failed apex seal, carbon chunks, detonation fragments), running the engine with inadequate lubrication, or severe overheating that warps the housing and allows metal-to-metal contact.

Mild scoring can sometimes be polished out. Severe scoring requires rotor housing replacement. Used housings in good condition run $300-800 each. New housings (when available) are $600-1,200 each. The 12A uses two rotor housings.

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.

Short trips where the engine never reaches full operating temperature, low-rpm driving (the rotary needs revs to stay clean), and poor fuel quality all contribute to carbon buildup. The rotary engine is particularly susceptible because the combustion chamber shape and seal arrangement create areas where deposits accumulate.

Prevention is key, drive the car hard regularly, use quality fuel, and keep the engine at operating temperature. For established deposits, an "Italian tune-up" (sustained high-rpm driving) can clear some buildup. Severe cases require engine disassembly and manual cleaning. Some owners use decarbonising additives, but these are controversial in the rotary community.

The front inner guards corrode from trapped mud, moisture, and road debris. Rust perforates the inner guard panels, weakening the structural support for the front suspension mounts.

The inner guard design traps debris and moisture in areas with poor drainage. Factory corrosion protection on 1970s Japanese cars was minimal. Decades of accumulated grime holds moisture against the metal.

Mild surface rust: wire brush, rust converter, and protective coating. Perforation: cut and weld repair panels. No reproduction inner guards are available, all repair work is custom fabrication. Cost: $1,000-3,000 per side for professional fabrication and welding.