Cooling System Inadequacy
Symptoms
The engine overheats, particularly in traffic, on hot days, or under sustained load. The temperature gauge climbs, coolant may boil over, and the engine suffers heat distortion or blown coolant seals.
Cause
The 10A produces substantial waste heat relative to its displacement. The R100's original cooling system, a single-row brass radiator, mechanical fan, and period water pump, was adequate for 1960s Japanese conditions. In Australian summer traffic, it is marginal. After 50 years of corrosion and degradation, it is often inadequate.
Fix
Upgrade to an aluminium radiator (custom fabrication required, no off-the-shelf option).
Fit an electric fan with a temperature-controlled relay.
Replace the thermostat.
Replace all hoses.
Ensure the water pump is functioning and its seal is intact.
Use quality coolant at the correct concentration.
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