QuestionQUESTION: When i first bought the car the temperature gauge always goes to hot within 5mins when the car warms up, but the car did not overheat till my radiator started leaking and blow my head gasket. I had to replace the had gasket and the radiator, cooling sensor and the thermostat. The car runs but when it begins to warm up, for about 5mints the temperature gauge goes to hot. The car is not loosing any coolant or leaking from anywhere. The radiator fans work when the car is warmed up.A mechanic told me it might be the water pump, but there is no signs of leak.
ANSWER: What model Mazda?
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QUESTION: It is a 96 Mazda 626
AnswerNot my area of expertise though some thoughts.
Never ever let a car's temp gauge go to hot. Shut it down and look for a fault or (as in your case) you'll be wasting money fixing heat damaged parts.
What causes overheats in a nut shell,
Air flow, lack of it from a as simple as a shopping bag stuck in front of the condenser to a bad fan. 12 volt fans can fail and still spin. You fans need to spin with force to draw in air while the car is standing still or moving slow in traffic. Check them well.
Coolant, Coolant Level and Coolant flow, Be sure to use a 50/50 or 70/30 mix (water/glycol) an excessive mix of coolant will reduce heat exchange.
Level, some systems (again not a 626 person) have air bleed valves to remove excess air in the system. Air trapped within can cause the system to overheat. When in absence of a bleed valve, raise the front of the car as high as possible and run it cap off topping as needed as you allow air to escape. Once full close it and top the reservoir.
Coolant flow, you should be able to see the coolant flow once the engine is at temperature with the cap off. The coolant must make it from the motor to the radiator and back for the system to work. Reasons for no flow (or a lack of) stuck or non functioning thermostat, sediment in the radiator, pump impeller failure, excessive corrosion in the cross over tubes both radiator and heater core.
If you have taken good care of the cooling system during it's life corrosion should not be an issue however, if you (or a previous owner) have neglected it and the coolant resembled oil or mud then you have problems and only removal and core cleaning or replacement can solve that.
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