In 90% of the cases, coolant leaks are the culprits that cause overheating.
Please check out our coolant leak page here:
FC3S Pro - Problems #1, Engine, Coolant Leaks
If possible, get an aftermarket water temp gauge to confirm the engine is
overheating. Relying on the stock water temp gauge is not a real good
indicator of accurate water temperatures.
Since the cooling system is not very complex, we can tackle other possibilities
one component at a time.
FC3S Pro - Problems #2, Engine, Thermostat
Radiator cap -
FC3S Pro - Problems #2, Engine, Radiator Caps
Water pump -
FC3S Pro - Problems #2, Engine, Water Pump
FC3S Pro - Problems #2, Engine, Radiator
Water pump housing - corrosion can degrade the water pump housing enough
to affect the water pump efficiency. Inspect the water pump housing
surface directly across from the water pump impellers. This surface should
be machined smooth without any pitting or grooving.
Replace water pump housing
Stock viscous fan -
FC3S Pro - Problems #2, Engine, Stock Viscous Fan
Water temp sensor - although rare, the water temp sensor can go bad.
The Mazda FSM has the temperature versus resistance table to check the sensor.
Replace water temp sensor
Bad engine - if all else fails, there's a possibility of a broken water
jacket or a bad water jacket o-ring. If coolant is being lost, and there
is no obvious leak anywhere, check the exhaust. If coolant is being spit
into the exhaust or you smell the sweet smell of burning coolant, it's pretty
much confirmed the engine is bad. Check to spark plugs for signs of
burning coolant - the tips should be very clean and / or white, frosted.
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